Warped grate on F500 - pics

i would say only way that is going to happen is with air coming threw the ash pan door this only normally happens when the stove is started with the ash pan door check the gasket on the ash pan door

If your not into burning everyday yet, i'd be inclined to taking the grate out and bringing it to the stove shop and comparing it to a grate on the showroom floor.

First time I'm seeing this, but what begreen pointed out is apparently a common problem with the Jotul ash pan design. Little bits of ash fall behind the pan, and collect over time. Eventually, your pan won't slide all the way back in the tray, affecting your gasket seal on the ash pan door. This was one of the many problems the previous owner had with the Jotul Firelight I inherited.

Surprising the grate buckled, though. Mine are both "keystone" in cross-section, as is the corresponding recess in the floor of the stove. If my grate tried to expand, it would almost certainly just pop out of the recess, not buckle like that.

Any time I clean the ash pan, I clean out the "tray" the ash pan resides in. It's an actual functional use for the hearth brush/broom the previous owners of our place left behind. And since it sat directly on the hearthpad, not hung up, it has a nice "bend" to the bristles, so it's good for reaching back and grabbing ashes that miss the pan.

I always clean out behind the ash pan when removing it to empty the ashes on my Oslo. It needs to be done with as little fire as possible and you need to do it quickly if there is much fire still in the box as it doesn't take long to enter "blast furnace mode" with the ash door open. This causes an annoying harmonic roar and can't be good for the stove. My grate still looks good, though.