So this issue has been brought up a few times here so I thought I'd share my approach to correcting/preventing it.
Backstory: I was mowing along just fine a few days ago and my PTO cut off for no obvious reason. Seat switch and reverse switch have been disabled so that work was immediately suspect. Those checked out so I moved on to the brake switch which was fine. I was generally looking around at the circuit board on the right side (Control/Fuse Module I believe it's called) and discovered that moving the harness caused a red LED to flicker on and off.
Long story short:
Cleaned them with this stuff and a toothbrush:
And added some of this to the contact surfaces:
I did the same to each of the safety switches mentioned above and the two relays below that circuit board. All is well now and I have a bit of confidence that it'll stay that way.
NOTE: DON'T use dielectric compound on contacts!! I've seen a few people say that this is a good idea. Just no!