I'd be wary of force multiple, it's hiding the error rather than fixing it. It's most likely that there are two or more functions or global variables with the same name which the linker doesn't like, force multiple will ignore that there are too many and just use one, but it might not be the right one (they might have different behavior despite the same name).
Microsoft's documentation for it says: "The /FORCE option can create an executable that crashes or misbehaves at runtime if it references an undefined symbol or, when a multiply defined symbol has different definitions, if it invokes an unexpected definition in context."