I've moved from a Windows 10 to a Windows 11 machine but I kept the same My Movies Collection Manager V5.40. I restored the database and all looks good except I get quite frequent "Changes have been made to your collection, would you like to synchronize now?". After clicking yes and waiting a few minutes I get a "your collection is already synchronized". Sometime I can make a few changes before I get the sync prompts other times I get it even after simple attempts to change data. I have a single instance of the app running, no active mobile apps.

There are no other active clients. I even uninstalled the Collection Manager on the previous server to ensure it would not interfere.

I completely uninstalled Collection Manager from the old server and, since your last post, I shut it down just in case a lingering thread was keeping it alive. I've made several change to the collection without the sync prompt until an update to a title failed as reported on a different thread ("Unable to modify any title on Windows Server 2016 MyMovies"). Immediately after the update fail, when trying to make a collection change I am getting promped to sync. Already happen twice to make it more than just a simple coincidence.

So when the call to update a title fails on the MyMovies server side it will update the online collection but not the local one leaving it out of sync even if there is a single server?