Alternative Curriculum rooms show as ??? in lesson monitor

[JohnRMoore]

Hi, I have exported and alternative curriculum structure to SIMS and populated it with a few students. The students timetables look fine, the staff timetables look fine, the room timetables look fine. When I go to lesson monitor, I can find all of these classes and the correct room shows for all. But when I open and then close the register to reveal the timetable view for that staff member, SOME of the rooms on SOME periods shows as ??? instead of showing the room code. I can't spot any pattern apart from all of the rooms do this before a random day next week. Does anyone know in what circumstances lesson monitor shows ??? for a room?

 

Thanks

 

John