When a spectator is viewing the map during an AVR update, sometimes (50%) of the time the view become messed up with the active vessel rendered on top of the map view like so:

http://imgur.com/zJGpYkt

The rest of the time the view will switch to vessel view no problem. It would be better to let spectators stay in map view across AVR updates though.

Workaround is switching back to vessel view, but that is still bugged with map view render artifacts:
http://imgur.com/i7pLMUI

This appears to be fixed as of 9ab0413.