Help. So I have this custom-made beaut that features an 18-volt Basstec onboard pre and all I did was change the batteries. Upon plugging her in and playing her last night, I noticed some static and slight "popping". Did some moderate to heavy slapping and, eventually, it started "farting" (loudly!), even when just doing fingerstyle plucking. It wasn't the amp and it wasn't a matter of clipping as I checked the levels and tried it out on different amps - all with identical results. This is the first time ANYTHING like this has happened with this bass. Like I said, all I did was change the two 9-volts. Any ideas?