Hey there, I had a similar issue with my 2015 Porsche Cayman S last year. The symptoms you're describing sound exactly like what I experienced, especially that grinding noise and unpredictable shifting. Turned out it was indeed the TCU. Took it to my local Porsche dealership after the warning lights came on. They ran a diagnostic and confirmed the TCU was defective. Had to leave the car there for about four days while they replaced the unit and reprogrammed the system. It's definitely not a DIY job, you need specialized Porsche diagnostic equipment to properly code the new TCU. It was a serious issue that needed immediate attention to prevent any potential damage to the transmission itself. Since the fix, my transmission has been shifting smoothly with no issues whatsoever. My advice? Don't wait on this one. Get it checked at an authorized Porsche service center, they have the right tools and expertise for these specific transmission issues. Best of luck!

Thanks for sharing your experience! Really helpful to hear someone else went through this. I'm glad it worked out well with the TCU replacement. Just curious, do you remember roughly how much you ended up paying for the whole job? And has everything been running smoothly since then, or have you noticed any other quirks?

Hey again! Yeah, happy to help! Since you asked about the costs, I ended up paying 1000€ for the TCU replacement and programming at my Porsche dealership. And I've got great news, everything has been running absolutely perfect since the repair! The transmission shifts like a dream now, no more grinding or slipping issues at all. It's been about a year since I got it fixed, and honestly, it was worth every penny. The car feels like new again, and I haven't had a single transmission-related problem since. My advice was spot on about going to an authorized dealer, they really knew what they were doing with the TCU programming. It's such a relief when these things get sorted properly, right? The peace of mind alone was worth it. If you're still having those symptoms, definitely get it checked out, sounds exactly like what I dealt with, and the fix is pretty straightforward once you're in the right hands. Let me know if you need any other details about the repair process!

Thanks so much for all the details! Actually, I bit the bullet and took your advice, got it checked at the authorized Porsche center last week. You were spot on, it was the TCU! Ended up costing me around 1200€, a bit more than yours, but I guess prices vary. The funny thing is, while I was there, the mechanic found a small oil leak they fixed for free since I was already getting work done. Talk about luck! The whole experience was way better than I expected. They even gave me a detailed walkthrough of what they were doing and why. The car's running like a dream now, smooth shifts, no more grinding, and that annoying slipping is completely gone. Should've done this weeks ago instead of worrying about it. Thanks again for pushing me in the right direction. Sometimes you just need that extra nudge to make the right call! Take care and happy driving!