It’s time for an update:
I’ve created a new database and connected it to my Strapi project. It’s working now!
Who can tell me what might have caused this problem?
While it’s good to know that it wasn’t Strapi causing the issue, I now have to transfer all my data to the new database, which is a very tedious task.
Problem solved! “INSERT INTO public” was created as a column in the table. I’m not sure what caused it, but I deleted the wrong columns. Now it’s working again.