Tiptronic Boxster Won't Go Into Park - Cable seems fine

[Sirius]

I'm happy to post that I found a solution to this problem. I had the same problem on my 1998 Boxster. The first problem I found was the linkage to the NSS. I replaced it and soon realized this was not the only problem.

The next problem was the Shift piston in the Valve body. Don’t worry it was easy to replace and it cost $23.00 Shipped. I have attached a link to an article that explains it all. It says 1997 only but mine is a 1998, it may be an early 1998 so that could be the reason I had the same problem.
https://www.transmissiondigest.com/1997-zf-manual-valves/
I hope this helps you!

[EJS]

I own a 97 Boxster equipped with the Tiptronic (ZF5HP19 / A86.00) transmission. I am experiencing heat related shifter/interlock problems. As the operating temperature rises, the Shift Selector becomes very difficult to move and does not consistently engage the proper gear. Eventually the car will not start in P until it cools down. When in gear, the transmission performs flawlessly.

After driving during a hot day, the shifter became extremely stiff. It eventually moved to N but would not move to P without considerable force. The shift linkage attaching ball socket was broken at transmission shift pivot. Shift linkage was replaced, but still unable to engage gears. Pan was dropped and the shift linkage pin was not attached to the valve body selector valve. The linkage was reattached and adjusted. This made the car road worthy, but did not address the heat related problem.

The transmission digest link that Sirius posted on 12/26/22 seems to match my problem exactly. Sirius mentions this valve can be replaced. Can anyone advise where a replacement selector valve / shift piston can be obtained?