I've had my 830 for over a year and a half and it's been in the shop 3 times for problems regarding the sensors in the upper and lower bobbin. It's rather the Achilles Heel of the machine. And it sounds like your machine has the same problem. It's a simple fix of replacing the sensors. The threading system in mine was also replaced. I don't know about feet not working as all mine work...that doesn't sound right to me. After the 3 fixes, my machine has been a joy to work with and I'm enjoying it immensely. But, there was a time I had buyers remorse about it. Luckily, my dealer is awesome with great techs and I've bonded to it completely by now. If you're not happy, make sure your dealer knows about the problems and is given the chance to MAKE you happy. The machine is the cream of the crop, and I hope you can get it fixed.