No this is not correct. Need more info to help. If the wiring is correct sounds like you have MPU board issues. Corrosion damage? Batteries mounted off board?

Was it working before?
Do you mean in coil test when a specific flasher goes off a different coil fires? Please explain in a little more detail. Is the problem repeatable or random?

Big guns was made at a time when the System 11B MPU was being phased in, so it can have either a System 11A or System 11B board. You can find schematics for either of these boards online, by looking a comparable time period games.