Check the 28 pin socket.
I recently ordered both the Gorf and the Galaga highscore kits from highscoresaves. I had trouble with the socket they supplied, and ordered round hole tin machined sockets from mouser, and everything worked great after that. I was getting stuck on screens, and sometimes would get garbled images.
That said,
I can't get over how awesome Joe is. He also talked to me for about ten minutes to help me with my kit.
Awesome highscore save kits.
I've mentioned that the OEM sockets don't seem to grip the socket that he provides as a riser very well. I use machine pin strips to overcome that. The same goes for the z80 ribbon cable. The pins are pretty thin.
