Video Playback is good, but general performance is SUPER LAGGY and UNRESPONSIVE

This is an odd issue I've never really seen or  noticed before.  The performance of PP on my machine lately has been soooooo laggy.  Video playback is totally solid.  No dropped frames at all.  Gone through and done all of the performance optimization stuff but can't see to figure it out.

Mostly seeing it manifest in the vu meter not really moving, the play/pause takes a second or two to respond (sometimes it gets hung and I have to wait for up to 10 seconds for it to pause after hitting space).  Just driving me nuts and having a serious effect on my productivity.

Running a RED 5k sequence with 3 or 4 tracks of video, not typically more than 2 stacked at any one time.

Running a 2017 iMac pro with OS 12.0.1.  64 gb of ram, radeon pro vega 64 16gb GP
On PP 15.4.1

Anyone having similar issues?  Nothing in my setup has changed.  Be working on this same project for months and it only started a week or two ago.