I mod your original app because I cannot generate a vpk on the kit it just include one character in the asset. After I modify the characters when its vs the Kung fu man it works but after the new characters are vs each other the game would crash.
I see, then it really seems like it happens when trying to load a stage that doesn't exist. That would explain why it works vs Kung-Fu Man, as his stage, kfm.def, should be included.
Could I see your data/select.def ? There might be something there that causes a wrong stage to load. And a link to one of the characters you use would be helpful, just to make sure it's not also anything else going wrong. Thanks a lot!