Thanks, I'll look into it... arguments checking is a relatively new thing compared to how long the YaruFPS code base has been around. I don't remember exactly how the script works, it might be that it uses the same argument signature as the other collide scripts but doesn't actually USE all the arguments.
Viewing post in YaruFPS Basic FPS Engine comments
Yeah, I looked into the code and there's commented-out code that used argument0 in the script. Change the first line into "var a = argument0, b = argument1;" (instead of "var a = argument1;") and the error should be fixed. (The collision scripts need a certain format because they're called using script_execute() depending on the object's terrain type, but not every script uses both arguments)