I'm getting same issue with Xcode 11.4 for UICollectionView and UITableView components in a macCatalyst hybrid app that uses UIScene multi window management. Tested the older code (before enabling macCatalyst support and the new scene management) and works fine in Xcode 11.4. Cleaning/rebuilding sometimes helps but most of the times it doesn't. What makes it worse ( in terms of frequency) is building for MacCatalyst and then for iPad/iPhone.Somehow seems to be related to having in the storyboards the Mac trait active. Just tried rebuilding several times with iPhone or iPad trait as default in those storyboards and each time it worked. I ll keep observing it over next days.