Some unknown 500 error due to weird block nonsense?

one of these blocks is creating a 500 error of some sort every time we try to save the page it’s on:

{
        "content": {
            "location": "kirby",
            "image": [
                "projects-directory.png"
            ],
            "src": "",
            "alt": "",
            "caption": "",
            "link": "",
            "ratio": "",
            "crop": "false"
        },
        "id": "c35ed1a4-7b00-46ff-a08f-1bf603c54b55",
        "isHidden": false,
        "type": "image"
    },
    {
        "content": {
            "text": "<p><strong>On MAC OSX:</strong></p>"
        },
        "id": "a54d7a27-8010-4502-972e-0612f3f4013d",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>/Users/xxx/Library/ApplicationSupport/Quantitative Imaging/QiTissue/QiProjects<br></p>"
        },
        "id": "9c12b731-9a3b-464e-a370-e2668a6c379c",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p><strong>On Windows:</strong></p>"
        },
        "id": "30baddfe-3184-4f2e-982a-bd843c7aa1ea",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>C:\\Users\\xxx\\AppData\\Local\\Quantitative Imaging\\QiTissue\\Projects</p>"
        },
        "id": "5f487941-712d-4e75-a4e3-af5bab0736f0",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>Contains:</p>"
        },
        "id": "1da6b4c1-2ab1-40c1-b670-dcb455ac5ddf",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<ol><li><p><strong>Log file</strong> (logs all actions and can be used to share with developers for debugging.)<br>Example:<br>QiTissue_2.0.0 Prerelease Version_2019-11-23T03-20-57.log<br></p></li><li><p>The locally <strong>changed biomarkers</strong> (when you make a change in the <a href=\"http://application.qitissue.com/documentation/reference-browsers#Biomarker-Reference\" rel=\"noopener noreferrer nofollow\">biomarker reference window</a>, this is where the changes are stored.)<br>Example:<br>biomarkers.json<br></p></li><li><p><strong>Custom Feature panels</strong> (if you create custom combination of features.)<br>Example:<br>featurePanels.json<br></p></li><li><p><strong>QiProjects</strong> folder (These show the that are listed in the Project Browser window. Not editable, but can be deleted.</p></li></ol>"
        },
        "id": "78e1589f-73dc-4813-b6a3-c4685018a5fe",
        "isHidden": false,
        "type": "list"
    },
    {
        "content": {
            "text": "User Data Directory"
        },
        "id": "f9c6e62c-a7e6-480c-a0b1-e8c283e4cc34",
        "isHidden": false,
        "type": "section-header"
    },
    {
        "content": {
            "text": "<p>How to get there using QiTissue…</p>"
        },
        "id": "e48550bf-3639-42fc-9fde-1307a5d32d93",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p><br>Preferences Dialog &gt; General &gt; User Data Directory &gt; push <em>Show In Finder</em> button</p>"
        },
        "id": "105cb191-e5e0-49b5-a8da-bc86febb438f",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p><strong><br>On MAC OSX:</strong></p>"
        },
        "id": "d6537671-9431-47df-9bee-a3786b629ccb",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>/Users/xxx/Documents/QiData<br></p>"
        },
        "id": "8371af8f-43f0-456d-9e05-4d1305e9ecdb",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p><strong>On Windows:</strong></p>"
        },
        "id": "edcc5aa7-9690-49af-8250-b311d507e769",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>C:\\Users\\xxx\\Documents\\QiData</p>"
        },
        "id": "8897ab7d-7dd7-4ed2-b7e8-48bab4f8b270",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>Contains:</p>"
        },
        "id": "31e40f15-c0f1-4e35-a4be-51d194b90915",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<ol><li><p><strong>Data for each image</strong><br>Example:</p></li></ol>"
        },
        "id": "755c1bf8-f6ef-4d85-8032-444f83338852",
        "isHidden": false,
        "type": "list"
    },
    {
        "content": {
            "location": "kirby",
            "image": [
                "qidata_example.jpg"
            ],
            "src": "",
            "alt": "",
            "caption": "",
            "link": "",
            "ratio": "",
            "crop": "false"
        },
        "id": "a9557795-8752-4250-a0ae-49f6f6298e69",
        "isHidden": false,
        "type": "image"
    },
    {
        "content": {
            "text": "<p>This includes the import and export folders and the computed features and cellmaps</p>"
        },
        "id": "ae388c06-9c4d-45c5-8b70-c649397d2567",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "Image Cache Directory"
        },
        "id": "a4af0d3d-8049-480c-915e-6cb0106abafa",
        "isHidden": false,
        "type": "section-header"
    },
    {
        "content": {
            "text": "<p>How to get there using QiTissue…</p>"
        },
        "id": "c2a88d57-f57a-4d3f-a06d-13cfb7effae8",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p><br>Preferences Dialog &gt; Memory Management &gt; Cache &gt; push <em>Show In Finder</em> button</p>"
        },
        "id": "6082298d-4bd7-4943-b88e-91f2e411229c",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "location": "kirby",
            "image": [
                "pref-primary-cache.png"
            ],
            "src": "",
            "alt": "",
            "caption": "",
            "link": "",
            "ratio": "",
            "crop": "false"
        },
        "id": "733c38b6-d2e0-48f7-aebc-844f2f6d478e",
        "isHidden": false,
        "type": "image"
    },
    {
        "content": {
            "text": "<p><strong>On MAC OSX:</strong></p>"
        },
        "id": "eae08ebc-6d21-4a7c-a92a-ff7ec1d1e252",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>/Users/xxx/Library/Caches/Quantitative Imaging/QiTissue</p>"
        },
        "id": "362e3007-124f-4779-84db-0ab5d3392876",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p><strong>On Windows:</strong></p>"
        },
        "id": "eb0f44eb-d2c1-49e8-97e8-804aaf00d3b0",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>C:\\Quantitative Imaging\\QiTissue\\Cache</p>"
        },
        "id": "28af2e76-3e40-4fd6-b83b-cb0345e626e3",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p><br>Contains:</p>"
        },
        "id": "3a491567-2875-4395-84f3-acf7021d1311",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<ol><li><p><strong>Cached image data, metadata, and processing pipelines</strong><br>like:<br>6c447782b1d96332a82ac26e69832dd91f54f36f.qiMetadataCache<br>074046eb76a3213da100264a6e73f9b0665f8059.qiPipeline<br>309dc7080312b9b0a44fe5c76978029d92b1c924.324c8ea00a7530792212a87c59523e220ca189cc.qiData</p></li></ol>"
        },
        "id": "02e299c2-2f32-4d53-bb60-2d5291553fa1",
        "isHidden": false,
        "type": "list"
    },
    {
        "content": {
            "text": "Shortcut to access hidden folders"
        },
        "id": "7abca122-fea0-4655-b33b-32333731367f",
        "isHidden": false,
        "type": "section-header"
    },
    {
        "content": {
            "text": "<p><strong>Mac</strong></p>"
        },
        "id": "8c2995f4-d6e8-4b44-a029-8e29ed42f20b",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>Live files are usually stored in three locations: the Application Support, Caches and Preferences folders contained within the user level Library on Mac (Macintosh HD/Users/[your username]/Library):</p>"
        },
        "id": "99cf18b8-73ba-4b1c-a817-acc87c5060c4",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<ol><li><p>Open Finder.</p></li><li><p>Click \"Go\" on the menu bar.</p></li><li><p>Press and hold the “option/alt” key.</p></li><li><p>Click the \"Library\" shortcut which appears.</p></li><li><p>Then navigate to the relevant folder (Application Support, Caches or Preferences)</p></li></ol>"
        },
        "id": "b2ab64ca-100a-4533-aa55-6885abff06a3",
        "isHidden": false,
        "type": "list"
    },
    {
        "content": {
            "text": "<p><strong>Windows</strong></p>"
        },
        "id": "c1f53839-85b2-46a1-a0b7-6c86f8841b9d",
        "isHidden": false,
        "type": "text"
    },
    {
        "content": {
            "text": "<p>Refer to this useful site for help finding hidden folders on Windows:</p>"
        },
        "id": "b42b5632-c380-437c-a0a0-4ef2a42568dd",
        "isHidden": false,
        "type": "text"
    }

the error looks like this:

we know it’s in those blocks because removing them from the [template].txt file stopped the error from occurring.

we are… very stuck on what the problem could even be, let alone what to look for.
also for some reason changing the page title in the panel is allowable, but any other field throws that error?

Is there any more information in the browser console (make sure debugging is turned on in your config).

Have you ruled out it has anything to do with your custom block type?

given that a section-header is one of the few blocks left that did work, and they’re working on every other page, yes we’ve essentially ruled that out.
devtools give me nothing not already visible, other than that the error has something to do with the panel’s app.js file, line 1 (which doesn’t mean much given it’s not pretty-printed)?
and a violation about document.write(), which is only used in that file

Have you tried to remove and then re-add the blocks one by one to find the culprit? Maybe some weird hidden characters somewhere…

we’re trying that now, just figured that anyone who does happen to know the problem perhaps could have spotted it before us

the worst part? it works fine locally, so we have to test it on the remote server.
also means it probably has something to do with the plugin we have set up to push content changes to a git repo, because that’s the only difference from what we do locally