I am getting the same result on CloudLinux 7.1.
If I disable ModSecurity the problem goes away.
Did you manage to find a fix for it? Is it happening for anyone else?
I have a CloudLinux 7 server that I want to install Plesk on. If I install 12.5 Preview and setup a few sites for testing, then can that be upgraded/switched to production with a genuine license key when it is released?
Or will it be a wipe and reinstall?
Look forward to your response.