[Screen customization plugin] Cannot delete any custom field created

Hello,
I had this error while watching the Apache error log

[Thu Sep 22 10:47:54.009767 2022] [:error] [pid 8505] [client 172.25.26.17:37198] PHP Fatal error: Cannot declare class UserMain, because the name is already in use in /var/www/html/projeqtor/model/UserMain_old20210628.php on line 0, referer: projeqtor.xxxxxxxx.xx/view/main.php

For some reason, the Projeqtor used "UserMain_old20210628.php" while having userMain.php just under it

Renaming the old file to ".php.back" and restarting Apache fixed the problem

While I'm searching for why it still used an old file, the suppression of custom fields works again now.

Thank you