power door lock problem 2000 s-10

I have power door locks, keyless entry...
when I use the remote to lock the doors, I have no problems. If I hit the lock button from inside the truck, the lock goes down then pops right back up again (driver side only). This started as an intermittent problem and I thought it was related to cold but now it does it all the time even when warm. Could this be the relay? I guess what Im wondering is, is there a dedicated manual(or other) relay for the button in the truck only? This would explain why it only locks with the remote.

Is your key in the ignition?If it is the door won't lock.

same problem when key is not in ignition...