Is it a software bug?

[M5Addict]

I recently took my car for a problem related to the revs increasing and then dropping without any change in speed, gear change or throttle input.

The software was updated and that problem cured. However, I then noticed the back of the car would swing out at the rear as though traction was turned off when it wasn't, on hard acceleration. Just didn't feel the same. It's now day 14 and the tyres are being suspected when they are fine. I don't scare easy and the car behaves like a monster. Traction kicks but not quickly enough.

Anyone experienced this or got any ideas? Want my car back and am desperate and fed up. Not had car now for 24 calendar days...