Afflicted with unprompted zoom-outs to full timeline.

Still having to constantly reset timeline to a view that allows me to edit. I'm using MacBook Pro. operating system 10.13.6. fcpx 10.4.6 The track pad is faulty so I use magic mouse.
When I begin editing, the system zooms out automatically so that clips are minute and large portion of very long timeline visible in screen. Checked to see if custom shortcuts was problem, but it's set to default in preferences. Some days, like today, the problem is continuous and began as soon as I started the session. Other days it seems intermittent and random.
Any suggestions appreciated. R

yep noticed the same on 2020 5k iMac (Apple Q&A has been lacking for quite some time)