I have a clone GDemu (not sure of the version but I want to say it's v5.5), and the only issue that I've run into is with Sega Rally 2. I'd say about 20-30% of the time when loading the game, it hangs on the SEGA loading screen after the DC logo. The GDemu reset button works to bring it back to the menu, but it's a pain because it doesn't seem to be predictable and requires restarting until it works.
I've turned off "force VGA" in the settings, and have swapped out the rom a few times to make sure it's not an issue with that. I'm running the DC through a Kaico Dreamcast-HDMI adapter if that makes a difference.
Does anybody know why this would be happening, or if there's something I need to do? It's not a huge deal, but it's sort of bizarre because it's the only game I've tried that's had this issue. Everything else seems to work flawlessly.