Classic Key fob problem

Hi guys, after 3 years of locking the doors with the key I decided to invest in 4 new batteries for the key fobs.
One flashes the ir light when the button is pressed, but when used to lock, the doors lock then immediately unlock, the other fob only flashes the ir light when I take the cover off & stick my thumb across the 2 large pc lines inside so I presume it is knackered. Any ideas as to why the doors dont stay locked would be appreciated. Just tried it again & it sets the alarm, but the doors still unlock immediately after they lock.

How freely does the sill lock move? Could be something is jamming. Or microswitch acting up on the latch?

I had this on my 1992 Classic....

The rod to the sill locking button was the problem, what was happening was the solenoid would pull the lock down, but the rod to the sill button was a fraction to short and it would pull on the lock and as such the lock thought the sill button was being lifted and as such unlocked the door again!

Thanks guys, when unlocking with the key one of the rear doors sometimes needs a second lock & unlock, must be that. Cheers.