Glad to hear you found and fixed it.
Your post reminded me of a similar issue I had with Firefox for....years, I'd say....until I stumbled on the cause by accident. Most detail and text is too small for my old eyes on my 21" monitor that I run at 1920X1080. So I set the scaling in Windows 10 to 150% - have done it for years. But there is one exception to that, one program that runs off the screen at that scale and can't be adapted to run compatibly with it - Railroad Tycoon II 😉.
So back to Firefox. When I started Firefox, it would (almost) always open to a mini-rectangle at the top of the screen (along with the standard taskbar icon) and I would have to single click it twice to expand to normal. I gave up trying to figure out why and just lived with it for a long time. Then one day recently I opened it immediately after running RRTII at its required 100% scale. There it was - full screen (with little tiny text), no extra clicking required.
That was it! It opened with its modified version of "minimized" because of my scaling setting. Opens normally when set at 100% for younger eyes. 🙂 I had experienced that from time to time before (which is why I said "almost" above), but never made the connection 'til just the other day.