I was experiencing a certain crash when loading a stage.
After the game crash I was presented with this error log.

./Data/LScripts/Classes/CWeapon.lua:298:ClientTick2
./Data/LScripts/Main/Game.lua:678:Tick2
./Data/LScripts/Main/Game.lua:1591:Game_Tick2

I had a back and forth with GoG support and while they were amazing in both response time and their willingess to help, I could solve my problem.

What I ended up doing is I snooped around looking for the first error in the CWeapon.lua file.
Line 298 on CWeapon.lua: "local back = 0.3 + (Cfg.WeaponFOV/100)"

There is nothing wrong with this line so I thought that the Cfg.WeaponFOV was set to a weird value.
I went over to Cfg.lua and I figured out that the variable WeaponFOV was never even declared...
I added this line right after line 219.

WeaponFOV = -10,

The problem was fixed!


TL:DR:
If you are having this error:


./Data/LScripts/Classes/CWeapon.lua:298:ClientTick2
./Data/LScripts/Main/Game.lua:678:Tick2
./Data/LScripts/Main/Game.lua:1591:Game_Tick2

Simply add this line after line 219 on Data/LSCRIPTS/Main/Cfg.lua in the game's installation folder :

WeaponFOV = -10,

Just a comment to mark the Question as solved so people can find it if they need it