audi A6 C7 3.0 TDI quattro gearbox concerns

[CraigT007]

I have had this car since new and over the last month has developed a worsening gearchange with the auto 's tronic' box. I've never had an issue before, but the gear changes can be (say maybe one in every twenty) very harsh and abrupt. Today I had real bother inching in and out of a multi story car park, release brake, expect to move... nothing, then a surge forward.
The car has been remapped so I've resisted software updates for a few years.
Could this be a software update fix, or does it sound more serious? I'd imagine a very expensive repair if the gearbox needs changed. The car has 55k miles on it and it is driven relatively easy by my wife, for probably 40/55k miles.

Anyone able to comment? Thanks