If you create a module using the Pagebuilder and then want to save it, this error appears:
0 preg_match_all(): Argument #2 ($subject) must be of type string, stdClass given
The module is saved and also appears in the correct position.
But if you want to change it, the same error appears again.
The module will also not checked in.
Tested on Xampp
Joomla 3.9.27, SPB 3.7.11 Pro and PHP8
Same also with Joomla 4RC1
Perhaps it could also be a Joomla problem, as this error is also displayed with SPB 3.7.10 (not tested with a fresh SPB installation - only downgrade).