Rear bushes are shockingly bad. Had mine changed and ended up paying over £300 for the privilege
My auto box had the exact same behaviour under the exact same conditions - I never bothered with it, as for 99.5% of the time it was perfectly alright, and I'll be damned if I'm paying £1500+ for a reconditioned box to fix what is only a minor niggle!
The term "software" is a bit misleading. All of the code that is used is "flashed" into non-volatile memory, so won't be affected. The only stuff that will be wiped is the stuff that the car has "learned" - as said above, window anti-pinch, sunroof setting, radio code (along with your saved stations and any EQ settings), clock, climate control settings etc., nothing that can't be reprogrammed in about five minutes flat.
Doing this also resets the engine map to a factory default, so the
has to re-learn everything - drive it around for a few miles and it'll sort itself out. It also has an effect on your fuel sensor too, so if you're using optimax, you'll find the car will take a little while to re-adjust for the higher octane fuel. Not that I think Optimax makes a spot of difference in the V6 anyway!
Hope you get it sorted - like I said before, mine did this for the best part of three years, and it never worried me too much.