While not being a highly qualified user of QCAD yet, I suggest that it would be necessary to set the "reference point" within the data being copied, relevant to the "from drawing" first. Then the "reference point" should travel with the copied data, to allow "exact" placement within the drawing you are ciopying to.
It is my opinion, that all drawings within the .dxf file are related to a single "zero reference point", I may be wrong, but that is my reading of the "DXF" file construction.
Somebody will, no doubt, jump in to tell me, if I am incorrect in my conclusion.
Hope this may help.
There are two types of "zero reference points"
1. " Absolute zero" : being the main reference to which all the drawing data relates.
2. "Relative Zero " : being the placement of data anywhere relative to the drawing's original " Absolute Zero".
I think that is how it is all glued together and stays that way