Korge SP-250 Electronic Piano

I have an SP-250 in for repair, it has an annoying static crashes on the Right Channel, Left Channel is perfectly fine and quiet. But the right channel is always making static crashes, not horribly loud but very annoying, I have checked the usual things such as lose solder connections, hot components etc and have also tried heat on various components such as transistors, capacitors etc but makes no difference, the static crashes are still there and do not seem to get any worse even with heat, I have replaced the Op Amp but again, no change. It sounds very similar to a leaky transistor as there were some older transistors that would give static crashes and it was due to the material used at the time but I did not see any of those transistors but always possible there was another batch with defective internal makeup over time. Anyone have any thoughts on this problem? Thank you