Editing files in iOS apps not saving

I’m not sure if this is an issue with the app I’m using or an issue with Nextcloud files app integration, but here’s what’s happening…

I use Clip Studio Paint to edit images in iPad pro, and I save the *.CLIP files on Nextcloud. Up until about iOS 15 everything was fine then suddenly I cannot save my work.

Now when I open a CLIP file and make changed, if I click save the app reports that my work in indeed saved but in reality none of the changes have been saved and when the app closes the file in the same state it was opened.

When I have the folder open next to the app so I can see what happens when I click save, the file disappears for about 10 seconds upon saving and the old version takes its place.

I don’t have this problem with other cloud providers so I suspect it’s a Nextcloud app issue.

Can anyone confirm?