The TX series of second stages (and I'm guessing probably the ATX as well) are easily opened for inspection and cleaning. Just twist off the faceplate in the palm of your hand, remove the diaphram and it's plastic holder, and you can see all of the internals of your regulator. This can be done while connected to the tank with the air turned on as well. You should be able to see any trapped sand, mud, lost tourists, etc, and wipe them out with a cotton stick, or rinse with water (but don't blast it under a faucet!). DON'T press the purge lever while the reg is NOT under pressure, as you risk water or grit entering your regulator internals. I do this after every dive just to check my regs aren't contaminated, and it's amazing how much sand can get in there if you're shore diving and there's a bit of surf about.
I think I've been in America too long, I actually typed faucet instead of tap(!).