An update.

So the OP sent me the .dwg file and I tried to open it using AutoCAD 2017, 2018, Dwg TrueView and even Draftsight but had no luck. I then asked him if he had a .bak file to share. He did and sent it to me. I renamed the file and opened it. There was his drawing. But, as I am always likely to do, I ran Overkill, -Purge (twice) and Audit on the file. I took a drawing file size of over 2.4MB and got it down to 860KB roughly. The Audit command found and fixed over 6600 errors in the drawing database. I won't bore you with the details of the junk for the first two commands removed. With a little more effort I could probably get the drawing file size down some more.