I've noticed that running DML via SneekDI has higher game compatibility than running it via NeoGamma, and one more thing, I can confirm that even compressed or shrink game works pretty well, RE3: Nemesis (compressed) does not work on NeoGamma but running it via SneekDI works perfectly without issues or anything.
Is your disc spinning the whole time? Do you use a gamecube or wii disc? If a game works shrunk or not depends on the game, one game that works shrunk does not mean all do.
Does it still work in Sneek+DI if you remove the disc after getting the 1st screen from the game?