rear running lights out

hello all ,

with good fuses & new bulbs my rear running lights continue to fail me. fronts are OK and recently after noticing they were out, they magically fixed themselves but my coworker advised the other day they are OUT again. dimmer switch was changed and new stereo installed recently , but I checked all connections in the areas that I recently worked on.

Haynes manual doesn't have the proper diagram to trace the lights. are there any alternate points I can check ?
thanks in advance for any help,
Sean

Same thing was happening with one of mine, and it turned out one of the plastic adapters was busted.... Taped them together, never had a problem since... Not sure yours is something so simple, but some kind of connection is def. it if they fix themselves.... Good luck!!