We upgraded from 2020 SP5 to 2021 SP4.1 this past weekend and have run into too many ghosts in the machine. The performance with larger assemblies and drawings is ridiculously poor, especially drawings. A sheet metal part drawing flat pattern will flip up on it's edge and when I click the "FLIP" button and it would right itself. I also have a large drawing with detail view circles randomly moving. When I fix, change sheet then back they will be moved once more. I do know I need to upgrade the files to match the version but that takes time. I also turned off the Enhanced Graphics which seems to have helped the speed but stability is way off. I am not really asking for advice or a "fix", just wanted to let users know what we are running into with 2021 SP4.1 (20 users with PDM Pro). Good luck fellow travelers.