A few more things. I searched the forum for other similar symptoms and it seems that
a)quite a few users are facing the same problem
b)wordpress has not officially come up with an answer saying “this is the problem and this is the fix”
nstead, I’ve read various possible things to do such as CHMOD files, change or even delete the .htaccess file or move it to the admin folder
None of the above solutions worked for me. My posts are 99% in Greek so its a bit difficult for any mod_security to be interfering with my server. Obviously I haven’t change anything on the code. Symptoms only appear when I try to post something or edit something as admin. When I logout and post as guest, everything is OK
https://www.nefsta-photography.com