Maybe something is wrong with mine. It seemed to work fine and gave a nice strong and clear signal on the games that worked. I think I used an Atari made power supply on it instead of the original. Was the Gemini PSU different?
I don't know, if some games are working great and some aren't working at all I'd suspect the design got closer with later revisions. It would be interesting to compare the circuit boards of your Gemini's and uptoknowngood's.