Premiere Pro Beta 15 build 27

Message to the developers. Whatever you did over the last 2 "builds" has bogged things down again. Prior to that 4k video was playing fairly smoothly at full resolution. No lag in the timeline when moving the playhead and hitting play in another section of the video. But over the course of the last two updates, it's now back to the less than stellar performance of 14.7, where you have to wait 15-20 seconds before the video starts playing again. What gives? 

iMac Pro, 3GHz 10-Core Intel Weon W, 64GB, Radeon Pro Vega 64 16GB, MacOS Big Sur 11.2.1.  

Moved from regular forum to the correct Beta forum