I have a few "shortcuts" (webpages as apps) that I run through the Brave browser, such as Youtube, or Protonmail....
I noticed this first in Protonmail: when I try to select text, or drag a message to another folder (ie click and then move my finger on the touchbar), the app immediately quits, as if I assigned "CMD + Q" action to this gesture (which of course I did not).
The only way this does not happen is if I "disable all gestures" for the given app.
This would be OK, but then none of the global gestures work either, which is frustrating 
This happens only in Brave apps. Not Brave itself, nor any other apps.
I am working on an M1 Macbook Air, Big Sur 11.2.3, BTT v. 3.561