I have had this same issue on 2 computers, both running windows 10 and vectorworks '19.
When importing DWGs that are very large, like an entire cruise ship with all decks, or an entire major leage baseball stadium, vectorworks just freezes while importing, but does not give any errors to point to a cause. I had another person in our office with autocad open the files, and export them in smaller chunks, and then I was able to import those chunks all into the same VW file with no issue. So it doesn't seem to be any issue with the size of the vectorworks file, just with the amount of data being imported all at once.
One of the machines is an i5 laptop, 8GB of Ram, and a low end discrete nvidia graphics card with 1GB of VRAM.
The other machine is an i7 desktop with 24 GB of RAM and an Nvidia GTX930 I believe, with 2GB VRAM. It has the same issues with the same DWG files, no error messages, just freezing on import.
EDIT: for the record, I am aware that both of these machines are probably below the recommended spec for such large and detailed drawings, but that is not up to me, they are company machines, and we are typically only interested in small portions of the large drawings to add our production elements into.