I kind of have a hard time believing the trouble is really with the lock solenoid since they are a relatively simple device and usually can stand abuses much more than the electronics can that operate them. They can be tested real easy by manually applying power to them to see if they are working of not. I could see the problem really being caused by the reverse inductive kick action that happens when a coil is connected and then disconnected to power. Placing a capacitor across the solenoid coil would reduce that voltage. Looking at the video provided in the link I would guess that is what is causing the locks to relock after the command to unlock them is sent by the key fob. Checking the action using the inside switch should be done also as the trouble might actually be due to the key fob.