I installed my Pop and Lock PL5300 a few weeks ago, and have been pretty happy with it. I have the normal gripes about the quality of the plastics, but overall the price was right and my stuff is more secure.
Unfortunately after a few weeks of use, I noticed my Pop and Lock was beginning to lock itself, so I went out and did some investigating. I noticed that each time I pulled the handle the lock cylinder would turn 2-3 degrees counterclockwise. After about three times pulling the handle, the tailgate would lock and I'd have to use the key to get it open again.
I called Pop and Lock and spoke with Jason in tech support. He hadn't really heard of the problem before, and I was happy to work through troubleshooting the problem. He had me pull the tailgate cover and call him back so we could figure it out. After getting the tailgate cover off, I started messing with it on my own and noticed the problem almost immediately.
On the passenger's (right) side of the pop and lock, there is a Phillips head screw that attaches the actuator to the lock barrel assembly. It appeared that there was enough friction between the screw and the actuator, that each time I opened the tailgate, the friction would cause the barrel to turn a few degrees, eventually turning far enough to lock the tailgate.
I backed this screw off, and Viola! no more friction, the problem was, the screw was now fairly loose, and I was afraid that over time it might back out, and the whole assembly would fall apart.
I called Jason back and explained all this, and he mentioned they'd been vacillating on whether to put threadlocker on that screw, that some units had the threadlocker and others didn't. Clearly mine was one that did not.
So I went down to the auto parts and picked up some of the red (high strength) threadlocker, at Jason's suggestion. And proceeded to fix the problem.
So here's the how to:
#30 Torx wrench
Large Phillips head screw driver.
Red High Strength Threadlocker (Permatex or Loctite seem to be the most commonly available)
First off, pull the back cover on the tailgate. Remember that the screws that go along the upper edge of the tailgate have a larger washer, so make sure to set them aside separately.
After you've got the back cover off, locate the phillips head screw on the right (passenger's) side of the Pop and Lock.
You'll want to back this screw all the way out, and remove the entire actuator assembly. Try not to rotate the actuator or its constituent parts while you're taking thing apart, everything has to line up just right when you put it back together, and it will go together more easily if you can just drop it right back in.
With this assembly out, apply threadlocker to the bottom 1/4" or so of the screw.
Reinsert the assembly and make sure everything is lined up and nested back in properly. Tighten the screw, and the back off just enough that there is no friction between the screw and the actuator. Too much will cause play in the whole assembly, so try to find the happy medium.
After you think you've gotten it to the recommend tightness, try the handle a few times and make sure the phillips head screw is not turning when you pull the handle. Also put the key in and lock and unlock the Pop and Lock a few times to make sure there is not binding or weirdness.
Once you're happy with it, put things back together, and try to leave it alone hour or so to set up. This should solve the issue.