I have a teacher that uses the Promethean board that has, randomly, pen marks appear in the top right corner. Sometimes the teacher is using the pens elsewhere on the board but other times he is no where around the board. Also, his computer will log off his account randomly.
This problem is intermittent, but appears that it becoming more common.
We thought this ma have been caused by other devices, but everything in the room is corded (no rf transmissions by devices in the room) and the classroom next to this teacher does not have a board on the opposite side of the wall.