Sounds like the valve body problem in our VW Touareg (commonly manifests itself as a really hard shift from 4-5 or 5-4).
We have the valve body on order from this place. $695 is WAY cheaper than paying someone $4-5k to do a transmission.
I just looked at the place ours is on order from and they don't list Porsche. But. I did find this (same transmission as a passat)
5HP-19FL valve body rebuild DIY
This is where ours is coming from. You'll need to figure out which one yours is.