I'm not certain this is quite true either.
Am I understanding that you copied a sheet as such to have a duplicate sheet?
If so, I would not recommend doing that!
What I have done, to use the same schematic in multiple sheets was to add a new hierarchical sheet, or 4. Then used a text editor to copy the schematic elements into the "blank" new sheets.
I forget the details of the why of it, but I remember the simple copy and paste of sheets ended up wasting quite a bit of my time and the end result was starting over.