Have any of you guys come across a ND3933 where the control knobs have been distorted by heat?

On this one, "someone" did not latch the bottom two glass latches and I am assuming that the heat from the firebox, along with combustion gases, went under the fireplace and overheated the valve. I seem to remember the piezo melted on one of these, but that was years ago before I went out on my own and my memory isn't what it used to be.

I need to know why this happened before I replace the control valve, so I can assure the homeowner that they will not incur this expense again and that the FP is safe to operate.

Thanks guys !!