Debug should always be set to false on a production server, but if setting this to false doesn’t have any effect regarding the thumbs, then maybe the plugin doesn’t do anything different depending on that mode, I didn’t really study the source code thoroughly.
This setting should also always be set to false on production, but has nothing to do with the issue, just a security thing.
I currently have no other ideas, if that is all in the configs and there are no other plugins. but if you have the time, try to install a fresh Starterkit and check if that behaves as it should.
It usually just a matter of copying the files over to a server. The only thing that we don’t provide is the nginx config that corresponds to what is in the default .htaccess, but you should be able to use that from the other projects.
Which reminds me that it might be worth looking into this config and if it has any settings that might interfere with the thumbs.
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