Toolbar bizarrely and sporadically keeps changing its configuration

For the past few months I've been running into a problem where the toolbar layout is inexplicably and continuously changing itself. 

As much as I wish I could identify or recreate the problem, I have not observed any rhyme or reason for why or when it's doing it. I repeatedly have to restore it back to default, and yet it will eventually change again as several tools just disappear in to the abyss (e.g. the marquee tool will no longer have the dropdown to pick the selection shape).

At this point being gaslit by Photoshop is my only best explanation -- but I'm curious if anyone else has also encountered or noticed this and maybe has any insight.