Has nobody else had this problem? I'm trying to figure out whether it's caused by the game bar or by Baldur's Gate III itself. The game bar is probably set up to stop recording automatically when switching to a different application, including the desktop. So the core problem here is that Baldur's Gate III randomly switches to desktop view at times.
As stated above, normally just once per day - today I had it happen repeatedly at the beginning of the recording, which is especially annoying mid-cutscene, because the cutscene keeps playing even while the game is minimised. One time today it was probably caused by a popup from my antivirus software, though. When Dropbox gave me a popup a few days ago that was visible in-game, I refused to click it, because I knew doing so would take me back to the desktop and interrupt the recording. Luckily, that popup didn't become part of the recording, as far as I can tell, because the game bar indeed only records within one application at a time.