tail gate will not stay up

All the light work locks work with cop. When you push star button nothing happens. It lime a fuse is blown .

It has happened at least 8 times. I took it in and they say they don't know since there isn't an error code. It started at 10,000 miles and is still doing it at 20,000. This doesn't make since. Even if everything is computerized there has to be something technical going on. Would like this fixed before it's out of warranty. It just shuts off then I have to turn it back on again. And no it's not on auto. It has happened at different degrees and speeds.

Certified Pre Owned
purchased with 18K miles on the odometer.
No major repairs though I will be getting new tires next week.

I also had a 2002 highlander with the same issue.....what could be causing the brake pad and rotor failures.