You can continuously fire without the weapon flashing or disappearing.

: If the game crashes when using a weapon, the ROM might be corrupted. Try a fresh install of the Cadillacs and Dinosaurs Readjusted mod, which fixes many weapon-related bugs and sprite glitches.

Even with the "20 Gun" mod, your choice of character still impacts movement and special attacks: Mustapha Cairo

The user’s query asks for a "fix." This is the crux of the deep piece.