I'm a 108 junkie and have worked on a ton of electrical problems with these things. Very rare for the relay to die but it can happen. If you pull the bulbs out of the sockets entirely do the rears lights start working? Check ALL the fuses with the a test light, not a VOM. check the grounds on the tailights. Remember that the relay is designed to flash eratically if it thinks the bulbs are burned out. it's all load dependant. Until all four corners are working correctly the relay won't flash smoothly.