Just wait until it gets wet, or after you've laid on it for seemingly a very long time to get that transit bus from a slow drift into your lane ... the return of dying goose. I had one and tried everything - got so fed up that I've now got a Mini Beast 5 on it now. Happily tossed the HD Premium Horn and listed it here in a thread that ran on 'the worst upgrade you ever did". YMMV and I hope it does...
It's been wet plenty of times, spray with wd 40 after you ride in the rain.
Hope yours keeps working. I haven't had any problems with my horn even when I remounted it inside my left lower fairing by the shift lever. Works great, nice and loud but away from the rain, heat and vibration.. here are a couple pics....
Probably because where you mounted it, you probably drilled a small enough hole for the stud.