I have been diving with an Aquatica AD7000 housing (Nikon D700) for a couple of years now. Rinsed it after every dive. Worked the buttons, as well.
I experinced some minor leaks recently and went about replacing o-rings. This is not hard to do, just tedious.
All of the exterior knobs are alimunimun and have stainless steel set screws. These loosen easily, except for two of the knobs, (Exposure Compensation/Reset button and the subcommand dial knob) which have set screws that are definitly frozen and bonded.
I am perplexed. The sacrificial anode is doing its job. I didn't see any crud built up on these knobs. All the other knobs and set screws are fine. The other set screws may have had some sort of compound on them. Perhaps these lacked the compound. I use Tef-gel on nautical metalic connections that might seize. But I never thought to loosen the screws on this housing periodically.
This seems like a weakness in design when plastic knobs would suffice.
Any experience getting these undone? I've tried soaking in solvent, then vinegar and critic acid.