2004 BMW 745i harsh downshift

Hello all,

I have a 2004 BMW 745i. I purchased the car from an individual after having it checked out by an import mechanic, who said the car looked like it had been treated well. It has just under 80,000 miles and came with several service records. I've owned it now for around six months.
For the past few months I've noticed harsh downshifts as I come to a stop. It seems like the harsh downshifts appear after about 30 minutes of driving the car. I began noticing it more and more so I switched over to manual mode, where I determined that the harsh downshifts occur when I downshift from 3 to 2. It sounds like a hard 'clunk,' and it's difficult to determine what part of the car the sound is coming from. I can also feel a 'bump' when these harsh downshifts take place.
One thing I think is interesting is that when I switch over to manual and slow down while staying in 3rd, if I'm completely stopped, I can downshift from 3 to 2 without any harsh downshift at all. It's only when I'm moving that the harsh downshift occurs, regardless of whether I'm in normal, sport, or manual.
I've read numerous forums on the internet describing roughly the same issue, but I've not seen very many sure fixes for this problem. I had my mechanic check the car, and he stated that after a bit of research and test driving the car, I needed to change the guibo joint. The only thing that made me uncertain of this is that he claimed the harsh downshift was from 2 to 1. He did not switch over to manual as I did when I observed the harsh downshifts taking place from 3 to 2. He did tell me that if the harsh downshift was indeed from 3 to 2, that instead of a guibo issue, it would be a software issue that would have to be handled by BMW.

I realize this is a very common issue due to the fact that I've read countless forum threads on this same topic, however I'd like to know if anyone has had any success with the 3 to 2 downshifts after upgrading the software. Also, if it is the guibo, why are the harsh downshifts only from one gear to another? And could the harsh downshifts be damaging the car in some way?

Thank you.