EPIRBs can be set off by vibrations, so they are usually mounted to the wall of a boat, which minimises this.
AMSA said EPIRBS should be placed in a mounting bracket or a grab bag with flares and other safety equipment.
Read more here:
http://www.coffscoastadvocate.com.au/news/westpac-helicopter-tasked-after-distress-beacon-in/2872074/