I'm not sure how my setup must be different from yours.
When I set lightgun = mouse and dual_lightguns 0, then my device 1 aimtrack shows up as Gun 2 in mame and tracks on the screen as expected. My device 2 is totally unresponsive. I can't even set buttons with it.
When I set dual_lightguns 1, my device 1 shows up as gun 1 in mame and works as expected, and gun 2 remains unresponsive.
Previously I had the issue as you with Device 2 showing up as Gun 1 at the same time as Device 1 showing up as Gun 1.
Still no fix
