Sorry for the issue. I have a few ideas you can try.
I would suspect a corrupt sequence as a potential problem, as I had a similar issue yesterday on an updated project. Do other sequences in your project playback without issues? If so, can you try copying and pasting the contents of your existing sequence into a new sequence? That worked for me.
You can also try importing the sequence into a new project and see if that helps "rewire" your project. That can work too.
Finally, UI twitchiness can often be cured by resetting preferences. If you are tempted to do so, you may want to sync settings first so that any settings you need to keep will be preserved. Please return with any questions or comments. Hope we can help you with a solution.
No improvements, just steps backwards as usual.
Sorry about that. BTW, this is primarily a user-to-user forum. You can deliver feedback to the product team here.