Hello and welcome to JA!!!
I'm Billy and i will assist you with this.
You most probably have a short circuit causing this issue......
However, the first place to look, would be on the wiring harness near tailgate hinge.....this is known to cause problems.....
so check the wires, and inspect if any is loose, or short to earth (chassis), and repair the wires, and this should cure your problem.
Thank you, XXXXX XXXXX This seems to be a good advise and I will check as soon as my car can be accessed later this week, and give you feedback on result.