2000 Nissan Frontier Unlocks doors on it's own
 

I just bought 2000 Nissan Frontier Crew Cab V6 4x4. It appears to have a
"ghost" or gremlins.... When I get in the truck, I automatically lock the
doors, well, as I'm driving down the road, they unlock on their own. Also,
I can lock the vehicle w/the keyless remote & set the alarm, hear the
"beep", & come out a few minutes later & the truck is unlocked. Any
suggestions?