Transmission Issue

[didakaX5]

Hey folks,

I have '12 X5 3.5i that I got back in February and have this weird thing going on that even got the BMW dealer here stunned with it.
Here's what's going on: Car is fine when cold in the morning - upshifting and downshifting is like it's designed to work. Then it reaches a point where the issue I have is showing up when i get in stop-and-go traffic after the car has been driven for at least 30min.(sometimes it takes less if warmer outside, or longer on colder days). When slowing down to a stop, after the transmission has shifted up to 3rd or 4th gear, there i this violent shudder the RPM's drop to about 500 and immediately go up to 900 for about 2-3 seconds before it eventually evens out to 600rpm. When still at dead stop and when I release the brake, it feels like only in that moment the transmission finds the right gear to start going again. On occasions, the RPM's fluctuate up and down with about 100 in between. Here's a link to the video of what's going on.

https://www.youtube.com/watch?v=fY7BYJwI9vI

I had the car at the dealer for about 5 days and they performed the software flash update, but after the issue showed up again gave me the b.s. crap they couldn't figure it out and asked me to approve an amount to start replacing parts.
I just replaced the tranny fluid and filter, but yet no luck.

I hope one of you folks can help or give me an idea what this may be related to!