Jotul 3 ash lip falling off

Hello,

I'm new to this forum and I'm looking for some advice for a Jotul 3 (used) I recently bought. It is roughly 5 years old and in great shape. Only one problem. The ash lip will randomly fall off without provocation. I'm assuming metal contraction and/or expansion might have something to do with it. I would think the weight of the lip and the manner with which it installs (along with some contributing gravity) would hold it in place so I'm confused as to why it keeps falling off. Is there supposed to be a tension spring or perhaps a bolt to hold it in place? Any advice or knowledge would be greatly appreciated!

It is supposed to stay in place. However, it does come flying off, if you drop a block of wood on it. Of course, I wouldn't know anything about that at all.

All righty then. Thanks for the replies. I'm not certain, but I'm pretty sure I've lined it up and installed it correctly, lit a fire, fed the fire, napped, fed more to the fire, napped again when BAM! Off it came, unprovoked! The nerve! Scared the b-Jesus out of the basset hound and me. This has happened 3 times. There is a hole on the rear flange where it inserts into the stove and (what appears to be) a corresponding threaded hole where both holes meet. Thought that threaded hole might be where an M8 - 1" mm (roughly) machine screw might go in? If thrice I don't succeed, I'll try, try again! Ill keep you posted should another nap be rudely interrupted again.