What is that loose thing inside at the top, a "cardboard" looking thing that lays on the "pipes" going across the top inside?
The loose sheet on top of the secondary burn tubes is the baffle. It needs to be treated with care and not poked at or hit with logs being loaded. The baffle is made of high-temp ceramic. Page 7 of the manual.
Just to clarify what you said about the "baffle", I was reading in another thread about a piece of fiberboard" between the burn tubes and the baffle. So maybe what I was feeling and moving around was a piece of fiberboard because the material did feel very lightweight like, well, like a piece of cardboard or rigid foamboard insulation---not heavy like a piece of tile. So in that case would it seem that the baffle was not displaced? I hope not, anyway.