Copy paste dimensions mystery

I opened a simple training file. Created a string dimension of all the windows in the level 1 view.

  lvl 1

Copied all but one windows to the level 2. Copied and paste aligned the dimension string. Revit omitted the dimension that referred to the missing window. That's fine. But the dimensions stayed as a string.

lvl 2

When I selected the dimension, Revit showed two locks for the missing dims.

Even though the dims were not visible (or there!) Revit thinks it is there.

lvl 2

When I clicked the EQ to make them equally constrained, Revit showed this:

  lvl 2

and an error msg that the wall conflicted with an insert...

I looked at the level 1 view....there IS the window!!!

lvl 1

It looks like, the one of the dim witness lines on level 2 is referring to the window on the lower level (level1).

When I copied and pasted the DIM string, revit attached all witness lines that had proper references, and for any witness lines that didnt get a reference in the pasted level, Revit kept the copied from reference and also made the dims not visible!