I've noticed there is a problem with TGE when I was playing through it. The problem is about pushwalls. In the DOS version, the pushwalls move 3 spaces, instead of 2. This is very important because there are some levels that if the pushwall doesn't advance far enough (2 spaces instead of 3), then one could be missing the secret bonus along with the treasure (and or enemies) behind it. One example is in Episode 5, level 7.
Perhaps the problem lies in the programming of the SDL version rather than the map design? I don't really know, but I thought I point it out since I've just recently discovered it.