Ok its great you got past the first problem, but now we have this new one.
This new one is weird, you are saying the document can’t be saved, or disappears from your tree? Or these aren’t resources in your tree? Not entirely familiar with Collections
If you can’t save the resource, you might want to ask your hoster if there are any errors on their side…any difference in your testing of hosters, with the different versions running fine?
Also pls check your Modx error log for anything useful, or anything at all probably.
Very odd behavior