After searching on Google, I found the issue appears in others Panels, and the culprit is:
ionCube.
Looking at the changelog, the 10.3.8 is supposed to include a fix for a potential crash with
OpCache. Looks like it's not enough.
To disable
ionCuble, removing the extension from
Select Options or disabling in
Manual Options is completely ignored by CWP for some reasons. I had to move the file
/opt/alt/php-fpm73/usr/php/php.d/iconuble.ini in a directory to not be parsed.
Once disabled, it works great again.