I've always felt an occasional kicking when upshifting with this car, but lately it really kicks like a mule, and a lot more often than before. What can be the cause of this, any ideas?

So a friend of mine suggested to check the transmission fluid level, but I reckon this gearbox (AT9) is maintenance-free, meaning I can't do it myself, right?

I had some similar issues with my 500X 2ltr Diesel, it was a Bent Cluth Fork caused by a loose ball bearing inside the clutch.

Mine was quite intermittant, but occasionally when accelerating away from 1st Gear, chnaging up into 2nd, it would suddenly race forward, and I would have to apply the Brake to stop it running away..

Dealership replaced the whole clutch as part of the Warrenty.

Well, I consulted with my service manager on this and he suggested a transmission checkup, which would include checking the fluid level and quality and recalibrating the gearbox "brain" (the control module). He said that recalibration helps in some cases. This will cost about 90 EUR, tax included. I think it's worth the money, because the issue has become quite bothersome.

UPDATE: They did the checkup last Thursday and everything was fine with the fluid, so they just recalibrated the "brains" controlling the gearbox. The half an hour drive back home from the service was fantastic, it felt like a different car, no jerking whatsoever, smooth switching and so on, but maybe it was a placebo effect or something, because the next morning the occasional jerking returned, although nowhere as "donkey-style" as before.

I've been watching the gearbox behavior closely these days and it's safe to say that overall the recalibration helped, having reduced the kicking considerably. It still happens sometimes, but it's barely noticeable and doesn't create much of a driving discomfort.