Issue loading modpack - duplicate mods false positive

[KundaPanda]

Describe the bug When I try to start the Hexxit-II modpack, FML crashes with the message "You have mod sources that are duplicate within your system."

To Reproduce Steps to reproduce the behavior:

1. Download Hexxit-II modpack using the Technic Launcher
2. Copy the modpack from the technic launcher folder to instances
3. Create config.json in the instance folder with the following content:

   {
   "loader": {
   "loaderType": "forge",
   "mcVersion": "1.12.2",
   "loaderVersion": "1.12.2-14.23.5.2855",
   "fileID": "1.0.0",
   "projectID": "hexxit-ii",
   "source": "curseforge",
   "sourceName": "Hexxit II"
   },
   "timePlayed": 0,
   "background": null,
   "mods": [
   ],
   "javaMemory": "8192",
   "lastPlayed": null
   }

4. Start GDLauncher and the modpack

Expected behavior The modpack should start

Possible solutions This might be an issue with the way instances are launched; from logs I can see that FML is using relative parent directories in the gameDir (--gameDir "....\instances\Hexxit II") and the crash happens because FML finds two "duplicate" (although they are the same file) files:

Found a duplicate mod voxelmap at [....\instances\Hexxit II\mods\forgemod_VoxelMap-1.9.28_for_1.12.2.jar, C:\Users\vojdo\AppData\Roaming\gdlauncher_next\instances\Hexxit II....\instances\Hexxit II\mods\forgemod_VoxelMap-1.9.28_for_1.12.2.jar]

which are resolved to the following absolute paths:

Duplicate Mods: voxelmap : C:\Users\vojdo\AppData\Roaming\gdlauncher_next\instances\Hexxit II....\instances\Hexxit II\mods\forgemod_VoxelMap-1.9.28_for_1.12.2.jar voxelmap : C:\Users\vojdo\AppData\Roaming\gdlauncher_next\instances\Hexxit II....\instances\Hexxit II\mods\forgemod_VoxelMap-1.9.28_for_1.12.2.jar

Screenshots debug.log

Operating System:

• OS: Windows
• Version: 11
• Java Version: OpenJDK 64-Bit Server VM, version 1.8.0_242
• Minecraft Version: 1.12.2
• Mod Loader: Forge

Additional context The fact that the instance is manually imported should not be an issue. The same thing happens when all mods are installed manually from the solder api-provided URLs.

[KundaPanda]

I tried starting the modpack again using the 'symlink' launch mode, and everything appears to be working, so this is only an issue of the default launch mode.

[Eskaan]

We have the symlink option for exactly this case