Same for us. Our channels went from vibrant to dead in a week because notifications are somehow broken there in ways I can't explain.

The solution for us was to create multi-user chats in the "Chat" section and let the "Teams" section die the horrible death it deserves.

The notifications are more consistent in "Chat". But god forbid someone talks too much, because then you get those horrible non-native notifications that are completely broken in itself too.

It's probably the worst app I've used in years, and that's saying a lot because app quality is incredibly bad these days.