I would have to agree with @rogerc, i wouldnt use silicon spray for the same reasons he has stated. Havnt tried his trick of heating the housing up etc, but it sounds like it would work.
I think any housing will have a sticking button at some point. Its wear and tear. But of course it shouldnt be happening with a new housing or one thats recently been repaired.
I have replaced quite a few o-rings etc on an aquatica AD7000 housing due to sticking. It was a little daunting at first, but its actually quite simple, and so long as you pressure test it without the camera inside, you shouldnt have too many issues.
Im not an expert, but as i understand it, its not only a silicone or o-ring issue in every cas. The actual shaft itself can wear and this causes friction and hence the sticking. So sometimes the whole button may need changing. But normally removing the piston and replacing the o-ring and adding some grease will do the trick. I used to soak all of the metal components in vinegar for about 30 seconds and rinse them off in fresh water.
