Okay, wow. I think I found something while looking at all the engine code. The nav-walking mode changes the settings of the capsule collider (object response of world static&dynamic) every tick to [Ignore] and after that back to what was before. But when the overlaps for the triggers are checked, it is changed to ignore and thus not recognized.
So your answer really is a workaround (I tried it again and now it works, maybe I didn’t compile correctly the first time… hehe…)
But when I setup a demo project with just a few AI characters and the same nav settings, it just works without the workaround.
So there has to be a cleaner way… somehow…