Different levels of group&ungroup Furniture problems, though not a big problem, but it should be corrected

I put A furniture on the first floor, second floor put B Furniture
Under normal circumstances it should be like this
Level1A

and Level 2B

2B Furniture is

original JPG
Then group 1A&2B like this

and

2B is Change

original JPG

Then ungroup 1A&2B like this,on Level 1A can see 2B


To solve this problem should not be too complicated:

then group, Record (2B) original ELEVATION

Then ungroup,Add a command, again the furniture back to its original floor.and set (2B) ELEVATION=original ELEVATION