My Lionel 027 remote gauge switch has been used in 10 years.  It only engages in one track.  The switch will not go to the other track.  I appreciate any thoughts

Confirmed that the switch model is 5121. 
Insulating pins are in correct position. 
The three wires on the controller are securely wired to the switch. 
When the power from the transformer is turned up, there is a grinding sound coming from the switch. 
When I attempt to use the controller to switch tracks, it appears to move slightly. 
When I use the manual lever on the switch, it operates smoothly.

Thank you

Larry,

Thanks for the info.  It solved my problem.  It was actually the correct location of insulator pins.  But you info was quite beneficial.  Great job!

Page 4 shows the location of the insulating pins.
https://www.lionelsupport.com/media/servicedocuments/70-5121-250.pdf


Larry