Figured I'd chime in here. I too have been following this issue, for what I want to say is 2+ years or so at this point. Was pretty frustrating even after multiple clean reinstalls, but I've managed to settle into a place where it doesn't seem to be bothering me as much.
I can't say for sure, but what I've done lately is not outright DELETE or RENAME any of the pre-made workspaces that come with Premiere. If there's a panel I don't ever use (like Learn), I move it into the Hidden or Overflow area. In the case I make a workspace similar to another one but rename it (I call one of my workspaces "Logging"), I hide the original, and create my new one.
I have to check when I get back home because I can't remember what all of my hidden panels are at home, but I recall that after deleting certain pre-made workspaces, that's when I noticed workspaces getting completely reset.
It's still not flawless: for example, opening different projects tends to have the Project panel pop-out randomly until I fix and resave the workspace. Not sure if Project panels are specifically remembering the name of the project or something - and I haven't been able to find a fix for that.
HOWEVER, I am not getting any complete resets of my workspace configuration. My top bar (knock on wood) has remained the same, and my custom workspaces are staying as is (minus the occasion project panel pop like I said).
Figured I'd pass that along in the event people get this issue consistently: try not deleting any pre-made workspaces and see if that helps?