If it's the shift rod position sensor, there are now a couple of aftermarket companies that sell replacement sensors (Porsche doesn't). So, you can have a new sensor installed for a lot less than a new trans -- just need to find a shop that can do the job. Or, if you wanted to do it yourself, it would make a great DV article.
Here's one:
https://t-design9.com/porsche_PDK_di...on_sensor.html
I've read a couple of cases on RL where the T-Design sensor fixed the trans. And they have more info on that page.
Good luck!