Breakout room preassignment

Hi. I’ve created the breakout rooms using pre-assignment feature. Before opening the breakout rooms, I see that the participants are correctly assigned. When I open the breakout rooms, however, there are always a handful of participants left out waiting in the main room. They do not see an invite to join the room. I’m manually moving 20+ individuals to their preassigned rooms everyday. I’m a Mac user. Could you help?