Is it me or have the last couple of beta releases got REALLY slow?

I'm on 22.0.0 Build 71, and I've noticed that the last couple of releases have really struggled with playback. I've been working on the same project for a week or so, on the same PC, same footage, same drives etc, but each time I've updated PPro, it's got more and more laggy and reluctant to play stuff back. For example, I have a 1920x1080 25fps sequence, with some 1920x1080 25fps footage in it - nothing too challenging. I've added a few 'Mister Horse' transitions (it adds two adjustment layers and a sound effect). In last week's PPro versions, it'd play back real-time, no problem, every time. In Build 71, I'm lucky if I see one frame of the transition. Nearly all my timeline is red (last week it was grren or yellow). I have a simple Lumetri grade on some of the shots - if I open the project in the public release version of PPro (15.4.1 Build 6), those shots are marked as yellow in the timeline and play back perfectly. The 'Mister Horse' transitions also play back perfectly (despite being red in the timeline).

Is there some issue with the beta version that will be fixed in the final release? Or is there some new, worse architecture behind the scenes that is breaking stuff?

My specs:

Windows 10.0.19043

CPU: AMD Ryzen 9 5950X 16-core

GPU: RTX3090 24GB VRAM (Nvidia drivers up to date)

RAM: 128GB

Footage is on a Samsung 980PRO 2TB M.2 drive.