i face this problem almost every time i re-mount the GPS holder. Atleast 2-3 times it falls. every time the holder falls, i try to put it in slightly different position. if it does not fall after driving for next 10-15 mins then i mount the GPS on the holder. till now i have been successful with this hit and trial method for the last 2.6 yrs! nowadays i try not to remove the holder from its place for this reason only. remove only the GPS whenever required.