Mine has been the exact same thing... the driver's side view mirror does the up-down-left-right movements every time I unlocked the car. It started to happen after I washed my car. I thought the setting was messed up somehow so I reset the key fob and even changed the batteries. It stopped and went back to normal. Today it was raining and it happened again and it happened to both of my key fobs. Like you said it has something to do with wet.
Please advise. Was yours eventually resolved?