I think this is a recent behaviour/bug. When bringing up the page selector by tapping either the top or bottom part of the screen, it would revert to a random previous page.
Support info:
Version: 3.13.6 Build 956 Env: Production
I have the same issue on the same version. Definitely a bug in a new release.
It seems the page selector is stuck on a page and doesn’t update where you were. If you then either mis-tap somewhere and open the page selector, it takes you back to the page it was stuck on. Similarly, if you minimised the app, go to another, then back to Panels, it’ll take you back to the stuck page.
However, if you browsed using the page selector, it will remember what page you left it on.
If you enable the experimental panels view, it doesn’t seem to occur but I haven’t used it much.
Now fixed in 3.13.7