[Bug] Evo 3.1.30 TinyMCE4 4.1.12 Theme not work

[Nicola1971]

Summary

I recently updated two Evo 1.4x to Evo 3.1x with the migration module. Both have been updated to Evo 3.1.30 (from master branch?) and both have TinyMCE4 4.1.12.

Steps to reproduce.

If I try to change the theme, from the Evo System settings, it is not saved, it resets to "Advanced". Same problem if I try to change it from the user settings.
The problem is not present on sites with 3.1.29 and TinyMCE4 4.1.11

EvoCMS version

3.1.30

PHP version

8.1.29