Hi Sergei,
Thank you for contacting us!
Our team has tested creating questions and adding items from the Question Bank using the latest versions of WordPress and LearnPress, and we did not encounter the error you described.
The issue may be caused by a JavaScript conflict with caching plugins such as WP Rocket, LiteSpeed Cache and Autoptimize.
To help us identify the root cause, please either disable any caching plugins you are using, or temporarily switch to the default WordPress theme (e.g. Twenty Twenty-Five). Then try creating the questions again to see if the issue persists.
If so, please let us know and we will provide an alternative solution better suited to your needs.
Best regards,
Brianvu-tp