I have put my share of Transgo kits in 904s and 727s without any real problems. But when I tried to install the Transgo kit in my 518, I had nothing but problems. None of them were the same as yours, but several that I was not able to resolve. I finally had A&A build me a valve body and all is good.

If you can get an unmolested valve body somewhere, I would start with trying that and see what you have.