I am unable to unlock the rear door from key fob, I have to open from inside handle, once open and shut I can lock all doors from fob, but once again can not open rear door from fob, all other doors open in sequence correctly. I had removed the lock, could not see anything wrong but lubricated with wd 40, put the plug back on the lock function, so I put the door together again, and checked it worked correctly, but as soon as I reported to my wife of the success it stepped working again. Can you help with this problem, do I need to buy a new lock. or is there sum thing I am missing.