Hi
We have joomshaper pagebuilder and helix ultimate on all sites plus akeeba admintools and backup.
Those are pretty common extensions and many people have them together with sh404SEF, I don't see this as a problem.
I've seen this issue happening exactly twice in the last year or so. I got a backup of the site in its "broken" state and each time, a folder in /administrator/components/com_sh404sef had been removed, causing the problem. By "something" which noone could tell me what it was.
Note that the actual problem is not in the system plugin. The problem is that the code this plugin is referencing, needing, is located in a file that's missing from your server, causing the error when the system plugin tries to use it. There is no modification of the system plugin you can do to fix that problem. The problem is what's missing from sh404SEF itself.
The missing file or folder is located at:
/administrator/components/com_sh404sef/vendor/weeblr/wblib/v2/packages/factory.php
Does it exist on your server? does it have proper access permissions, ie the same as all other files in your Joomla installation?
Best regards
Yannick Gaultier
weeblr.com / @weeblr