Aruba TAC asked me of the placements. They are deployed in a modern office building in the ceiling using the brackets that accompany the AP's. The temperature is around 20-22 degrees Celcius, and the first ones fell off 3-4 months after deployment.
Might be we just got a batch with some faulty plastic.. We have other customers with many AP225's deployed in various locations which have not experienced this.
Adding a picture which are more or less identical to the OP's.