Thought about this little issue ages ago but it wasn't until riding in the rain yesterday that it popped into my head again.....although the SPOT is allegedly IPX7 waterproof.....
The cradle if mounted back on an angle or laying flat to give SPOT clear sky view can hold water from rain or washing until it evaporates......
So the simple fix.....drill a drain hole in the lowest point to suit your mounting method......simple I know but may save you a $200 replacement, if SPOT is laying in water for a few days until it evaporates
Cheers