It's a bug, and it's (supposedly) being worked on.
Also, Naffen and I were testing them on Mustafar the other day. The issue seems to be that they actually just won't go off around other players. I threw my bacta grenade in the same arc a few times with no one there, it went off. When there was a player within the radius of that arc, however, the bacta grenade would tumble uselessly. Sometimes it would go off when the player left the vicinity.
+1 If they actually told you to suggest this for some reason, though.