I have this Vermont Castings Defiant Encore model 2550. The catalytic combustor has apparently not been changed in 20 years and is probably completely gone. I ordered a new combustor and went to replace it, and I'm stymied at the first step. The instructions in the manual say "release the hood from the fireback by swinging the hood upward and then sliding it to either side". Sounds simple enough. The hood swings out a little bit - maybe an inch before it stops, hitting a lip above it. There is no way it is going to the left or right, as the sides of the hood hit these ribs that go up the fireback inside the edge of the hood. I banged around on it for more than an hour, and it's just not going anywhere. Something's not right here - but what? I can't think of anything to do but get in there with a Dremel and remove a bunch of metal until it has clearance to come out.