I am also occasionally having this issue. I am pretty sure it's the switch itself. I bought mine used from someone else. Since the switch that controls the trans shifting is no longer used in my truck after the engine swap, I may just swap them and see what happens.
1994 FZJ80. Elocked, MAF 3/2 Lift, BFG 315 KM2s, stock 4.10s, ARB bullbar and a Warn 8074 winch.
powered by an all-aluminum 335hp L33 Vortec V8
2004 Kona Stinky dee-lux.