I am getting Ajax error wtih (200) Problem saving file. I have uploaded the php file and the link I provide for mediacontroller is https, and the site is https. uploads and php files are chmod 750. The server is on gcloud, I have full access to the settings from a terminal (if I need to do some tinkering in the background I can).
That error message is returned when move_uploaded_file from line 37 in the PHP script fails. Did you create a subfolder named (exactly) uploads next to your .php file, and did you give it the right permissions (eg. chown -R www-data uploads/ and chmod -R 755 uploads/)?