Hi, we had the same issue. First I also tried downgrading back to version 3.8.10 but then we had a helix3 template error. After that, we upgraded the Page Builder with major version 4 and then to 5 and checked the server settings. The Joomla itself was on 4.3.1 so we upgraded it first to 4.4.10 and also raised the PHP version to 8.1 from 7.4 and after these steps, the latest version of SP Page Builder works fine now. Now we have also upgraded the web page to Joomla 5 and everything is fine and works as it should.
I think that the PHP and Joomla versions are the key. Check them if they're on PHP 8.1 and the Joomla is 4.4.10 at least.
I hope it helps you fixing the problem too.
FRIK