I recently moved a budget category into a new master category using YNAB 4 on my desktop. The category moved to the new master category on the iPhone app, but the master category balances did not properly update. I was able to correct this by changing sync method to WiFi and then back to Dropbox to force it to resynch. Appears this is not getting properly synced with the cloud synch system.
I don't move categories around often, so this is a rare issue for me, but wanted to report it just in case anyone else runs into the issue.