pop

Has anyone experienced a "pop" upon removing a regulator from the tank? - Regulator has DIN to Yoke adapter - Tank off - Second stages depressurized - Inflator depressurized Slight difficulty in turning the knob on the Yoke adapter, then "pop". I've used the regulator on multiple dives since...

I have a regulator that is only a couple years old. I had yearly maintenance done on it last fall. I tested it on a tank yesterday for the first time since getting it back from the shop and it'll make a hissing noise like its leaking air, then all of the sudden i hear a pop, and then it stops...