I had a miserable time with Gbox also. i bought their detent and mine would not come out so I kept calling them for help, and I mean after paying $175 for the small metal detent, I figure they could spend some time helping me but eventually they would not return my calls or contact me. I even sent them photos of my detent after I finally got it out: after removing the transmission and then the casing to remove the detent from the inside! It seems my detent was spread eagle at the bottom where the roller sits so there was no way it would ever come out the way it's supposed to from the top. The guy at Gbox apparently never had a clue that could happen. Admittedly mine was a strange case but it should still interest him but never heard from them again.
So I say to give the chinese version a try definitely especially for the price and if it works, that's great. If it doesn't, you can still buy a "better" detent but I think there's another Porsche specialist trans shop that sells one and I would use them as I'm sure they will be better with support and qurstions than Gbox!
Good luck!
Here's a pic of my old detent and why it would not come out: