So here's my uneducated guess. Four times in one week? It's the same guy. Hubturning. They know exactly who was in that room (and by the way, I wasn't working).

Or if it's different people in different rooms? It is a possibility that whomever is cleaning those rooms has a bit of hostility towards pilots. I've gotten some ugly looks from the cleaners, when all I did was say hello. Is it the same person reporting it?