I think many people who buy animated props are in your shoes, I know I am. Paying hundreds of dollars for a Gemmy or lower end animated prop is always a risk. I think that is why haunters graduate to making their own or buying a better made, more expensive prop.
I don't let people walk through my haunt because I get a huge volume of ToTs and can't control the herd. Many of my props that move and make sound don't get a chance to be really used, so don't feel like a broken prop is useless. Look at Pumpkinrot- he doesn't have any animated props, and his haunt is legendary.
Maybe somebody here can help you, but many times you will just have to take it apart and hope you can find something glaringly wrong and fix it. Someone here just fixed a Gemmy Cauldron Witch, so you never know.
Yeah my halloween yards been on pumpkin rots blog a few times (foggyfathoms). I make some of my own stuff but I just don't have time to fix all that's broken plus I'm not that good on working on those things really
Yeah that sucks. While these types of props aren't cheap, they are low end mass produced items. One of the biggest downfalls is that they can't tolerate being out in the weather. As far as finding someone to try and fix them, unless you can get someone who'll work on them for peanuts, it probably isn't worth the cost. Personally, I would purchase another Corn Stalker when the 2015 season gets close and keep your receipt. Wait a few days, box up the one that doesn't work and get a refund.