500 internal server error when adding block

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Hello all!

Recently I cant add any blocks in 5.6, it just has the add block window come up with a spinner that wont go away (and a white screen on the add block window), the error log shows that there is a 500 error:
GEThttp://xyz.net/index.php/tools/required/edit_area_popup.php?cID=1&a... 500 (Internal Server Error) jquery.js:4

I also some time have a 404 error that it cant load resources/demo/main.css in which case it doesnt produce the 500 error but the same thing occurs.

Thanks!