Flycast- dual mouse / lightgun button assignment problem on 2nd mouse/gun

First and foremost consider this:

• Only RetroArch bugs should be filed here. Not core bugs or game bugs
• This is not a forum or a help section, this is strictly developer oriented

Description

While playing lightgun games with Flycast core, i am able to map buttons on the 2nd lightgun (Sinden Lightgun) in the general INPUT menu but it is not recognize in the game.

Expected behavior

With lightgun #1 in port 1, every buttons can be mapped in retroarch general INPUT menu AND they are recognize ingame. This is not the case for the second Lightgun in port 2.

Actual behavior

Lightgun #1 work #1. I can map trigger, reload, start and select button as i wish.
Lightgun #2 aiming is ok using the proper mouse index. Trigger and reload are ok only if i map those buttons directly in the lightgun software/driver using left/right mouse buttons respectively. Other mapped buttons in general INPUT cannot be recognized (probably any other buttons as well)

Steps to reproduce the bug

1- In Retroarch, load Flycast core
2- in Retroarch general INPUT, set # maximum users to 2
3- Port 1: use proper mouse index
4- Port 1: map GUN Trigger, GUN Reload, GUN Start and GUN Select
5- Port 2: use proper mouse index
6- Port 2: map GUN Trigger, GUN Reload, GUN Start and GUN Select
7- Start game (ex. NAOMI HOTD2)
8- Quick menu
9- Select CONTROLS
10- change port 1 to Lightgun and port 2 to Lightgun
11- Lightgun 1 work normally. Lightgun 2 aiming is ok but buttons are not recognize.
12- alternative solution for Trigger and reload on port 2: in Lightgun driver/software, select Left mouse button for trigger, right mouse button for reload. This will work even if no mapping are set in Retroarch general INPUT port 2 menu.

Bisect Results

Version/Commit

You can find this information under Information/System Information

• RetroArch: 1.9.3

Environment information

• OS: Windows
• Compiler: original build from Retroarch site

Reproduce the issue on Windows with RetroArch 1.9.3, the Flycast core, two mouse or Sinden lightgun devices, and the listed port and control settings. Compare port 1 and port 2 mappings in the general INPUT menu and Quick Menu > CONTROLS. Done means port 2 aiming and all mapped trigger, reload, start, and select buttons work in the game without driver-level remapping.