It may simply be a grounding issue. All of the electronics may be perfectly fine. Remove the bridge and make sure there is a solid clean ground there on the bridge. The may require sanding some chrome off the bottom of the bridge to make sure you have good contact. You may also want strip the ground wire back a bit more or even sandwich in a piece shielding.
Check the ground wires at every connection to make sure there are no loose or cold solder connections.
