That is some impressive sleuthing. It never would have occurred to me that the issue was exacerbated by a switch to Mode 3 and the concomitant inability to control the drone in the intended fashion.
The same happened to me until I realized I was touching the left edge of the screen with my thumb which caused it to go back to the previous view - the start menu.
The reason for that is almost always because a thumb is inadvertently touching the tiny back arrow top left of the screen as it reaches across to the left stick. Minor holding technique adjustment required to avoid that, but once you get in the...
Are you sure?
If you have an RTH height set to 50-metres for example, that is 50-metres above takeoff point. If you were then flying 50-metres below takeoff point and hit RTH the drone will climb 100-metres before starting its return home.
Because it's a dumb thing to be doing.
You probably don't realise that many aircraft don't have ADSB-out and your app won't be warning you about them.
And the planes that don't have ADSB are mostly smaller planes which are the ones most likely...