'58 2.2D Sport Premium door locking issue

Hi I reset my locking by locking car normally then press both lock/unlock button - continue to hold buttons until you get the haz's flash then this should reset to double lock.
I have a another issue with the rear off-side door lock which I thought was the single/double lock problem but might be something else so I tried this - it works as listed in the manual but my problem is that if you double lock then next single open (driver door & boot) the rear off-side now also unlocks. This does not happen if I single lock !
Jag is x-type 2001 2.5 v6 sport auto

For no aparrent reason mine stopped double locking, it turned out to be the passenger door lock was stiff so I exercised the lock a few times manually with the door closed by pushing and pulling the little lever above the door opener and normal service was resumed. I surmised that if one lock gets stuck the double lock feature doesn't work - hope this helps