Elven ingot grinder?

Not sure if this is a bug, i've played at least 10 games so far each going down at least 4 levels. Two have went past level 7.

I've noticed if I did not manage to get the Elven ingot grinder in the first or second level, it does not spawn anymore on the deeper levels? Have anyone else encountered this?

 

They do seem to spawn less often than the other items. But I have seen them in earlier levels.

 

I think they only spawn on level 1 and 8, at least what i've noticed so far. Its quite frustrating if you did not manage to find any on ground level and have to grind all your way down before you can find another.