Error after update: 'INVALID_CLIENT: Invalid redirect URI'

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Describe the bug

After the remember me update, I can no longer login

Expected behavior

Get redirected to the dashboard

Additional context

The error I'm getting is "INVALID_CLIENT: Invalid redirect URI"
I've set and reset the API_ENDPOINT url multiple times by now, and I keep getting the same error.
I've rebuilt the image a couple of times by now, also to no avail.

Screenshots

The error:

The API Endpoint as set in the spotify dashboard:

The API_ENDPOINT in my docker-compose:

I've worked with docker before but that was a couple years ago, is there maybe a setting I'm missing?