Not your average neutral safty/mode selector switch problem
 

I have been a mechanic a long time. I have a prob . 99 Isuzu rodeo has wired shift problem. When in park dash shows park when in reverse it shows park when in neutral it shows nothing when in drive it shows low when in 3 or 2 it shows 2 and in low it shows low. I changed mode selector switch 3 times now and each time it works koeo then she drives it 100 yards and the lights screw up. Each time it's the same. Is this a possible ECM or tranny issue or maybe you have a diagnostic procedure I could grab from ya. Any advice would be helpful.

I have not seen this problem either but it almost sounds electrical problem.
When in the correct gear does it act up or it shifts fine????? have you done any work under the dash?? check your ground wires there is a main ground under the dash and also their is on next to the ECM try thoes....