Faulty Hu Card convertor or games?

[myoldskool]

I have a PAL Turbo Grafx and recently aquired a Hu Card Convertor that looks like the type available from TZD (the one made by Telegames). I have 7 games but two dont seem to work properly (Son Son II and Valkyrie No Densetsu) Son Son has a perfect title screen but either the player is invisible (but u can still see his spear when u push the button) or he is visible but cannot kill anything or be killed or jump on logs but he can climb the vines and be killed by lava. Valkyrie appears fine and then freezes amonst other things. Anyone know of a fix to these problems, I thought a cartridge game either works or it doesnt, not somewhwere in between!!! Any help would be greatly appreciated.