sounds like wires are getting pinched or rubbed when vehicle is moving ,Hmmmm,.Here`s another thought,check the bulbs closely .I had a 1157 bulb go bad many years ago in my truck.filament/element broke and crossed over to tailight element . blew the fuse ,spent a day on that little job before I found it. truck was only 3 years old.. maybe get another flasher and try it. And last but not least if you want to find short in a hurry pull the fuse and put in a jumper wire and look for the smoke ,when you see it you`ve found your problem. Don`t know if I`d do it but just depends on how fed up i was at the time. Have done it before on the Big trucks, lots of wire in those suckers. This info should get the techs fired up, Best bet tho is to start tracing the wires from the fuse box out .