Reviving a dead topic, but no-one seems to have an actual fix apart from "fix it".
If you've tried all the normal ways of fixing a drawing (purge, audit, exporttoautocad, copy into new dwg file) to no avail, then this might help you.
I encountered this issue today and after a bit of playing around with copying various parts of the drawing, I found that a block had a pdf underlay defined in it that had been removed but not purged before being made into a block, somewhere, somehow that pdf underlay was blown up to many times the size of the solar system and wasn't showing in the main drawing (this explains why a simple floor plan drawing was 115mb).
Save a copy of the drawing you're trying to copy from, open it and explode everything (run it 4 or 5 times), select everything using ctrl + a and then hold shift and deselect what you can see/what you want to copy, this will hopefully leave a couple of grip points selected, open the properties tab and find what the issue is, or simply delete the buggy entities, you might have to do this a couple of times
another issue i found during my investigations, there was a dimension style loaded that had the oblique set as their arrowheads, however they were a custom definition of an oblique, which i assume also contained the autocad oblique shape definition, i changed the arrowhead style to the regular autocad oblique and purged, solved the "duplicate definition of block _oblique ignored" warning.