seeing dms on another account

On my 2nd acc i have a few of the group chats from my main on my dms if i scroll all the way down. old messages show but it hasnt updated in 5 months. is this just like a display glitch? i would really not like for the people in those gcs on my main to accidentally see my 2nd acc. i left one of the gcs on my 2nd acc to see what would happen and there was no notification/indicator in the gc. i haven’t tried talking in them because idk what will happen. but still i’m paranoid. the same doesn’t happen the other way round though