4 windows + sunroof open by themselves

[R8DX5]

I've read a few threads over the years in which people return to their vehicles after work or in the morning to find all 4 windows down and their sunroof completely opened. Can anyone who has experienced this tell me what was the fix?

My GF just bought a new E90 and she has experienced it twice. The first time it happened it was raining and her car got all wet inside. She made an appointment with the dealer to have it checked out next week. However, being that this is an intermittent problem it might be difficult for the dealer to diagnose. I've read on a couple of other forums that it can sometimes take weeks to diagnose.

I tried searching this forum but nothing of value was returned.

Much appreciated.