There seems to be a bug in recent betas of Prem that will slow timeline navigation to a crawl when 'Show Duplicate Frame Markers' is enabled. This happens to me when the timeline is at a wide zoom and the squence is complex. I have been using MultiCam sequences with multi-track waveform audio files. Interestingly, if I delete the multi-track audio tracks in my sequence the slowness dissappears. I have tried converting the audio to various different formats and the problem persists. The issue is lessened at a narrow timeline zoom.
I am currently using Version 24.1.0 BETA (Build 38) on an M1 Max MacBook Pro 64GB. This has been happening for the last couple of weeks on every daily build of the beta.