Have checked the bulbs and wiring around the immediate area and can't see any signs of chafing or shorting.

Anyone encounter this?

 

First place I always look in these situations is any trailer wiring that may have been added to the truck by anyone. Also a good idea to take the trailer wiring connector right apart and look in the back of it. They tend to fill up with mud and gunk that can conduct electricity, as well as the wires can come loose from the pins and float around inside the connector causing all sorts of grief.

 

Awesome suggestion... The guy I got the truck from had wired the 4 wire trailer harness in wrong and it was blowing the reverse fuse...