When I opened your drawing I was notified it was created in another software not AutoCAD, and the blocks in your drawing are corrupted? Maybe this other software cannot work properly with dynamic blocks. Indeed copying those existing blocks does cause them to resize. But inserting the same block fresh into the drawing and changing it's features then copying that, works just fine, so it looks as though the problem is with this other software.
Unfortunately, if it's broke then you don't have many options, AutoCAD can't fix problems brought in from other software. But as a workaround rather than trying to copy the layer to a new drawing, I would try making a copy of the drawing and deleting everything else in the copy leaving just your blocks, and work from there, maybe they will behave working that way, but you might find they go wrong again sometime in the future, it really would be best to start fresh using AutoCAD blocks, but that is your choice.
