FCP: Second window suddenly on wrong screen, no way to change it back

I have three monitors set up on my Mac Studio.

The main ultrawide monitor is connected via USB-C. My main editing monitor is also connected via USB-C and hanging above the ultrawide. The third monitor is connected via HDMI and standing vertical on the left side of the other two monitors.

Over the past few months, I've used the ultrawide for the timeline, and the monitor above for viewer and rgb parade, since that is a HDR monitor and most of my workflow is HDR. For that I was always able to use the "second monitor" option in final cut and select viewer.

Since yesterday, without any updates or changes happening in between, the second screen is displayed on the left hand vertical monitor. There is no way I can change it. I can't grab the second screen and pull it over to the top monitor, I can't select "Window -> Move to.." (well I can select it but nothing happens); the timeline screen can be dragged and moved as I wish.

Yesterday I found a workaround by setting my desired second monitor for FCP as my main monitor in system preferences, however, today this also doesn't work anymore. Whatever I do, the second screen of Final Cut will open and stay on the wrong monitor, which is basically killing my workflow. I need the second screen on top for the HDR capabilities, and the left hand monitor can't just be disconnected, since I need it for editing notes and stuff (disconnecting the third monitor would obviously resolve this issue though). When I power the third screen off, the second screen moves to the correct monitor but get's instantly sent back as soon as the third monitor has power again.

What's strange is that I didn't change a thing. I didn't update to macOS 15 yet since I feared weird issues just like this, and my Mac hasn't been restarted in a few days, so there shouldn't even have been something updating in the background without me noticing.

Any ideas?

Update:

I shut down the Mac and started it up again, and now it works again. Maybe it depends on which monitor is starting up first to be determined if it's the second one? Would be the only idea I have. And I think there should be a way to select it manually..