Mesh creating odd shadows and acting odd when room is moved.

So I made these benches a couple years ago for a build then never used them again. Now I have a new build that needs them so I pulled them out of mothballs and thought about sharing them.  I put them in and everything seemed OK but when I went to move the room, the bleachers stayed behind.  The height is fine, they arent below ground. The other thing I noticed is that some of them have weird shadow flickering.  Ive tried moving them up and down with the same findings.  I am still very much a beginner so Id love if someone could take a look.

They are meshed from the  base game ottoman.  Maybe I should try merging it from a different mesh?  

Also, is there any quick way to add in rig slots for seating? Its exhausting when you have multiple seats and then adult, child and toddlers. Just figured Id ask.

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