Just bought a 50S this week to put on my gf's helmet. 

The unit will not locking properly on its base. In fact, it will fall off if I shake it a little bit while upside down. Afraid it will leave with the wind when riding .

Also, I do not hear anything in the speakers unless I press down on the unit while on its base...

Any idea what to do to ensure a good locking down  as well as fixing the sound issues ? 

Any help appreciated. Thanks