Verbal communication
When I was doing my training, we worked in a variety of different offices in order to gain experience of different departments.
The 'Contracts Office' was a half-floor with two cubicles, one for the 'Chief' and one for the 'Manager'. These two people despised each other and would not communicate except by passing notes through a sliding-hatchway, especially built for such purposes. They never visited each other's domain. The reason for the stand-off was lost in the sands of time.
For some reason, the Chief's office was always cold; the Manager's office was always hot and he had the window open, almost all year.
After the older of the two retired, the whole floor was refurbished and it was found that the room-thermostats, affixed to the adjoining wall, had been interchanged.