Michelle, Mike is right on this one, by what you describe it is guaranteed to be a faulty controller.
You say you don't want to spend $300 to repair a 9 year old vacuum? Don't be foolish! Even if you bought the vacuum used & didn't pay full price thru the in-home demonstration, you do realize this is a $3,000 dollar vacuum with a 25 to 30 year life expectancy, right? And if you did replace it with a quality canister vacuum, like a Miele or Sebo, anything even remotely close to the quality & performance of your Rainbow is going to be over $600, & closer to $1,000 new, with a 10 to 15 year life expectancy.
You made the investment in a quality cleaning system, now don't be cheap & just pay the money to get it repaired & have it for many years to come.
Rob