R129 won’t unlock with key fob from outside but will from inside ?

[parm]

Hi All having an odd issue with my R129. It won’t always unlock using the key fob from outside the car or lock in that case, but if I open it with the key and pres the lock button it will then almost always lock. Seems like the fob works in the car but not outside. Any suggestions on where to start trouble shooting please ? I’ve changed the batteries in both the fobs and same issue.

TIA