Hello Kevin,
I am working in a brand new project that has not been converted from a previous version and the problem persists.
We are working with 1440p .mp4 footage recorded in OBS from a Logitech webcam, and 1080p .ts files from an elgato game capture card. The framerates are the same, but the webcam footage drifts about 11 frames every hour, so the footage has been rate stretched to be in sync with the clap syncs and the beginning and end of the video. I've been using this same rate-stretch workflow for over a year now at this job, and it is only with the new update that the motion tool has stopped working.
It seems to be confused about what I am trying to click on. I am currently experiencing the issue right now, with two video layers (the webcam and the game footage), and every time I click and drag, the only thing that happens is the other video layer gets selected in the timeline. So with V2 selected, clicking and dragging selects V1, then I immediately click and drag again and V2 gets highlighted once again. Switching to another clip further down the timeline, moving that with the motion controls, and then coming back seemed to fix it.
I screen recorded it here: adobepremiere_motionissue.mp4 - Google Drive
As you can see it does not affect every clip. It seems very random and I have not found a means of replicating the issue. It's just randomly throughout my 30 minute timeline.