It sounds like when you CLOSED THE BLOCK EDITOR you forgot to SAVE the changes to the block.
When you want to use the block in the upper floor plan, use the INSERT command, then select it from the drop down menu of blocks which are already in the drawing, which you said you had redefined.
In that way you will get the one you want.
You need to be careful when creating blocks that the UNITS of the block are what you want them to be.
If the UNITS of a block are not of the same UNITS as the drawing into which it is inserted, then
it will be scaled accordingly. In this way blocks can be used across dimensional platforms (Metric or Imperial).
You don't want to EXPLODE the blocks in the block editor.