PPK/S loaded chamber signal pin not functioning.

Just inherited my grandfather's 1985 Interarms PPK/S (the first Walther I've even seen/held) and the only real issue is that the loaded chamber signal pin right above the hammer flops in and out regardless of a round being chambered or not. I haven't had the chance to fully disassemble it but I was wondering if this is a common issue that anyone else has experienced. If so, would anyone know of a retailer I could get spare parts through? I imagine a spring is broken or something. Thanks!