Reverse lamps inop

I have a 1996 Chevy K1500 P/U with a M/T. I have found that my reverse lamps do not work with the tranny in reverse. I know it is not the circuit as they work with the switch jumped and with the switch manually activated when removed from the transmission. To be sure it wasn't the switch I tried a new one anyway and they still do not work. Has anyone had any experience with this? I believe that the shift fork is what triggers the switch. I am wondering if maybe it is worn down or has too much play. I do not have any trouble engaging any gear. Thanks for reading this and for your help.