This was driving me crazy for weeks. I finally got it to act up while mowing today. When I went to adjust the deck height with the lever, it would engage the interlock.

I checked the wire harness near the lever engagement mechanism, and sure enough, 2 wires were pinched and cut. This looks like a poor manufacturing job of locating the wire harness. It appears after 9 years, it finally chewed thru. I solders and shkrink-tubed the 2 wires, and rerouted the wire harness away from the lever mechanism. Success!

That is 2 repairs this week!