Ok so to answer my own question... putting some insulating tape between the pcb connectors and the speaker resolves the directional lighting issue. Just for info, F0 controls forward marker lights, F1 controls the rear lights and F2 controls the cab lighting. There are 2 undocumented switches on the PCB that completely switch off all lighting at either end. I'm curious to know, what happens for a sound decoder? Are these lighting channels retained?