GameEx doesn't allow games that are not in a set to launch with Merge Sets Enabled

I am setting up my PS1 emulator, and I've got a problem. If I enable Merge Sets, games that aren't part of a set (games with a single disc) wont give the option to load. Games that have multiple discs (part of a set) and are of the same file format work perfectly fine so it isn't a filter problem. All my games are rar'd per image file (1 per disc) and they're all in the same directory. I'm using PCSX Reloaded, command lines are working fine and everything loads, GameEx just doesn't appear to see the game file unless they're part of a set, they still show up under the game list however, and all snaps/video/info work.

Just to clarify the disks are all in there own seperate .rar files and GameEx is merging the sets by the naming convention.