I see you are using Mechanical. Are any of those blocks Mechanical Structures? If so have they been modified and moved in your source drawing? If you have layers frozen within a structure then move those blocks around in your source drawing, the items on the frozen layer will not follow. Also any copies of that block will still have those frozen items tagging along but not where they belong but in the same reference point to the original part. Therefore, in your current drawing all the objects will be pasted with their layers thawed. You will see the frozen objects, (which are now thawed) in their "modified" position in the source drawing in your new drawing. I hope that makes sense.