Just to follow up - Julian and I were able to solve ueli's issues with installing.
Sometimes on macOS the "sudo" command breaks (I'm not sure how, but it's unrelated to installing Vectorworks). Our installer requires this tool to work. The installer tests for this now, and if it's broken will give an error message rather than doing a partial install.
You can test this by typing "sudo echo hello" in terminal. If it says something like "sudoers is world writable" then your system has this problem. If it asks for a password and echos the text "hello" back at you, it's working. There are some less common states where sudoers.d or other related objects may have improper permissions, but this is less common (this is also what "repair permissions" used to fix, but it seems like Apple has removed that functionality from diskutil in recent releases of macOS)
To fix sudo, we used finder to set permissions of the file /etc/sudoers to read-only. Once sudo is working, installation can proceed.