turn signal questions?

The flasher is not causing this problem — it cannot. It sits upstream of the turn signal switch and whenever a right or left turn signal circuit is completed by the turn signal switch, the flasher provides pulsed current. It has no way of knowing whether a right or left turn has been selected.

The problem is most likely in the turn signal switch, but faulty local grounds at the rear lamps and/or hacked wiring are worth checking into, as well.

I've got new turn signal switches if you need one.