However, I find the Traser/H3 stopwatch has "sticky" buttons and when flying holds (JAA IR training) it sometimes fails to start or stop
Interesting. The buttons on mine have a very positive 'click', with no hint of stickiness or binding.
It sounds like yours might have a problem with the sealing o-rings, or perhaps they've changed the design. (Mine is about 4 yrs old now)