Sorry I have to come again with the same issue because de case was closed without a solution. So I copy the issue again:

I installed a copy of the mainsite https://www.hlcollection.ch to https://www.room-concept.ch and upgraded to Joomla 4.4 and the latest SP Pagebuilder Pro Version.

Now the error "Class "JString" not found" shows on several pages in the frontend and also in the backend. https://www.room-concept.ch/index.php/de/jobs

ANSWER FROM RASHIDA:

Hi there!

Sorry for your experience.

I have checked your backend and found out there were helix3 framework too: https://prnt.sc/w_imZQt1eUvX

Helix Ultimate and Helix3 are two different frameworks from us and not recommended to use together in a single site at a time. Kindly uninstall all instances of Helix3 from your site. And then updaate all extensions.

Due to language barrier, I could not understand what types of page is bind to the 'Jobs' menu that shows the error. Will you let me know?

Best Regards

MY ANSWER:

Hi Rashida

Thanks for you reply. I have uninstalled Helix3 and now it shows this: https://www.room-concept.ch/index.php/en/about-us

It's in all languages the case. Here is the english version concerned. If I change the menu-point About-us to a Pagebuilder Page it works. The problem comes with standard articles.

Thanks for supporting me!

Since then, nothing. Maybe I change to Yootheme...