In any .cap with lots of events and lots of groups, occasionally clicking on an event or an action (To select it) will sometimes highlight all of the events in said group.
However, usually scrolling the event sheet up and down fixes this.
Consider this fairly low priority, just freaking annoying.
I do not have a .cap of this because, as far as I can tell, it randomly occurs, making it unreproducible.
It tends to happen after I've been working for a while though, after adding several objects and groups.