sound issues Spectrum LX bass

Hi all,
Did anyone have a problem like I'm having? Yesterday when practicing I had issues with my bass. Plugged into a DI box, into a church sound system I found that I was only getting some noise when the volume was full on. Ok, I thought it could be the batteries that needed replacing and yep, both were at around 8.5 volt. Duly replaced. Tried it tonite and still the same issue. The pull / push switch does not seem to make any issue. I do have an option at church playing a Hammer from Slammer but hey, it's not the same... What am I looking at? faulty switch? How do I test the switch?
Any info appreciated. email direct if want to zl1wt@xtra.co.nz

As a first step i'd clean all switches and jack ect. with a good quality switch cleaner and retest directly into an amp.

DO NOT use WD 40 or the like

+1
You wouldn't believe how many problems are caused by a bit of crud on a contact point. Absolutely no WD40!