S8 D2 erratic gearbox

[Snaggle57]

I've now realised this only happens when warm, after say 10-15miles.
Driving from cold it's lovely and smooth.
Could it be that the gearbox has the wrong oil in it? Or would it just misbehave all the time if that were the case?
It's had the oil / filter done but with 17 owners/ no history I dread to think by who
Has anyone else had experience of the wrong gearbox oil being used?
Thanks