Funny thing is I am the complete opposite of @kevtaylor and have had no problems with Delkims, from pouring rain to hot summer days, with either the ST's I have (promoted to pike fishing), and the TXi'd I use now for carp.
When I worked in a tackle shop we had quite a few Fox alarms had to be sent back for replacement in the original Micron range, although the Mini Micron's which had no sounder box at the time were not a problem.
Hopefully Fox updates have sorted out the problems, although I always wondered why they needed to 'upgrade' and replace the range every few years.