I'm a mechanic by trade, so when I hear metal on metal noises, I usually think there's something wrong or something is going to wear out too soon.
The noise the door latch made on my new Hitzer 354 was driving me nuts so I put some dielectric grease (see photo - any auto store has it) on the fixed roller and latch. It's been 2 weeks and the latch is still much quieter and operates a lot smoother.
Any grease may work but I believe this stuff handles the heat better and should last longer.
I also put it on the contact areas of the ash pan latch - works great.