Check out this thread from a fellow Brethren. He has identified the problem as a leaky damper door. This was suggested in the thread above also.
He has a nice solution that he says works well.
I do agree that for the price you should not have to do any mods for the smoker to hold a temperature, but this looks relatively easy and effective.
I'm also in the market for a new smoker and really wanted a Vault, but I've heard too many bad reports on their customer service, and my limited experience has convinced me that I don't want to deal with Pitmaker no matter how good their product.
I've sent 2 e-mail messages with some basic questions. Both were delivered and opened by Pitmaker, but I never received a reply. I guess I could call, but if a company has a customer service e-mail address I don't think it's unreasonable to expect a reply a week after receiving confirmation that they opened your e-mail.
For me it's going to be a Backwoods Gater once my budget can handle it. Less expensive, great product and wonderful support. Not as pretty as the Vault, but I'll learn to live with it!