mystery popping?

[cheezemaster]

I'm noticing a slight popping (occasionally) when I touch my strings or the bridge when using my bridge pup. It's not really loud and It doesn't happen all the time, but it's kind of annoying. Is this a ground issue? I has some trouble getting the solder to stick to the back of the pot, so I'm thinking this is the culprit - I've double checked, though and it seems to be affixed pretty solidly. Could it be an amp/electrical grounding issue?

Note- this is with my Custom P-90 where I swapped out the ceramics for alnico 5. Coud this popping be related to the magnet swap? I made sure to screw it back toghether tightly and It otherwise sounds great.