go through the connections in the headlight bucket and give them a good clean, and make sure the grounds are good on the nuts for the headlight ears.
do the same on the back tail light unit, and make sure that the signal stem is actually grounding the bulb consistently. if not you'll have to run a grounding wire from the bulb.
remember that it only takes one bulb improperly or sketchily wired to throw off the flasher relay.
good luck.