My mid-90s Defiant Encore has developed a crack & bulge in the fireback, which is pushing the combustion throat (I think that's the correct term, the plate that hangs on two ledges in front of the upper fireback) forward and causing it to fall off its ledges at the slightest provocation (a touch from a log). I hope my photos show the problem (taken with the combustion throat removed). Questions: - is this normal, or the result of over-heating? I'm not aware of having run the fire too hot. - can you get a new fireback, or repair the existing one in any way? If I could grind back the bulge that would make a big difference. Thanks in advance for any suggestions.