Here we go only a month back in a RRS - come back Audi all is forgiven!!

I pulled up Friday night outside my drive when the road was clear I pulled across the road to reverse back up on my drive (blocking the road as I always do) I turned the selector out of Sport to go in to reverse and only got as far as D it wouldn't go any further I turned back to S then D but that was all I was able to select D & S? So now I'm blocking both lanes across my road cars building up and a parked car not 12" from my front bumber! I couldn't go either way to get out of the way! In the end I switched off the engine (I know the car would go back in to P if switched off in D) I switched back on and was able to select R. I sat on my drive selecting D then R and so forth without a problem. The very next day exactly the same thing happened!! I called out LR Assist a very helpful guy called Simon arrived he was brilliant I have to say. After a long chat he plugged his computer in and gave the gearbox a software upgrade We took the car for an extensive test drive stopping and selecting R several times and it seemed as though the problem was solved! I went out this morning came home pulled across the road to reverse back in to my drive and again I was unable to select anything but D & S I tried going back to S then back to Drive, on the second attempt again I was unable to go any further than D but I lost my cool applied a far bit more brut force (good job I never had a large monkey wrench handy!) and it turned back down the gearbox

Anybody experienced this or have any suggestions?? Could be a sensor or a sticky selector???? Cheers Laurence.