Deere 655C - safety lever/machine travel malfunction

I've got a customer with a Deere 655C track loader. I'm not real familiar with these machines, this is only the 2nd one I've worked on much.

He was using it this afternoon and it came to a dead stop and the safety lever light lit up (like it does when the bar is down, in the parked position)

When I pulled the bar up to the run position the light goes out for about a split second then comes right back on. When it does this it won't let the machine travel. Boom still works fine fine but...

Deere 655C - safety lever/machine travel malfunction

Deere 655C - safety lever/machine travel malfunction