I agree with dougrainer, replacing that many parts is unusual. If it is something you can do, I'd pull that puppy out and check it out fully. Pull your board and have it checked at a RV shop. There are devices for doing that. If there isn't any board, pull and clean all the connections. Something weird is happening in your heater. Check Suburban's website for repair manuals. They may have them in PDF format. I'd PM Chris Bryant and ask him about trouble shooting and repair manuals in PDF.
On Edit:
For spadoctor, I'm so very sorry, I put down Suburban and not Atwood. Please change procedure to check Atwood on line and check with Bryant about Atwood heaters.