Update 3.2 to 3.3, panel problem on MAMP

Hi everyone.
I am checking back into a project on my local server (MAMP 5.6) that was put on hold in September/October 2019 and now is being picked up again so I decided to update from 3.2.5 to 3.3.(0/1/2/3rc1). The good: The whole website is working nicely in the frontend. My problem is the backend with one particular page only: that page (“FAQs”") has structured fields (and it has it´s own blueprint). In the panel on MAMP, trying to access that page produces the following error message:
“The JSON response from the API could not be parsed. Please check your API connection.” This message shows up from 3.3.0 up to 3.3.3rc1. The page has a sibling page (“Status”, standard, text, image, no structured fields), I can access that one in the panel with no problems.
Much to my surprise the problem only shows up on MAMP, if I upload the website to a live server, I can access it in the panel. The project has other pages with structured fields far more complex and they work fine and will display in the panel … Any clues where I could start looking?

You can get and share with us error details about which file and lines from browser console.

Is this what you´re referring to? This is the log from top->details->faqs


Fetch finished loading: GET "".
app.js:1 Fetch finished loading: GET "http://localhost:8888/website/api/pages/details?view=panel".
app.js:1 Fetch finished loading: GET "http://localhost:8888/website/api//pages/details/unlock".
app.js:1 Fetch finished loading: GET "http://localhost:8888/website/api//pages/details/lock".
app.js:1 Fetch finished loading: GET "http://localhost:8888/website/api/pages/details/sections/drafts?page=1".
app.js:1 Fetch finished loading: GET "http://localhost:8888/website/api/pages/details/sections/listed?page=1".
app.js:1 Fetch finished loading: GET "http://localhost:8888/website/api/pages/details+faqs?view=panel".