Choppy playback of 120fps footage at 50% speed.

I've upgraded to Premiere Pro 23.5. I've opened a project from January with a clip that is 120fps playing at 50%. When I exported in January I had smoth playback of the 120fps clip playing at 50%. Now that I need to export a version with a changed title the clip plays back choppy using Frame Sampling and I'm seeing the same frame 6 times before it moves to the next frame using Frame Blending and this problem is worse when using Optical Flow. When I export the timeline renders this way as well. I've cleared the cache and deleted render files.

I made a copy of that project and opened it in the public beta version. My slow motion playback is smooth but all of my audio volume keyframes are all set to 0 and the keyframes are not visible in effects controls. 

Why do updates to Premiere seem to break features that worked fine in the past?