Why does macOS Catalina install and/or update fail with "OSStatus error -37"?
I have a small internal drive in my 2018 Mac mini. So, I keep most of my data on a large external SSD. For ease-of-use, I replace most directories in the user home directories with symlinks. That way, for example, the ~/Documents dir points right over to a dir on the external SSD.
Well, I also use this symlink method for the /Users/Shared directory. It looks like:
&gt; cd /Users
&gt; ls -l | grep Shared
lrwxr-xr-x  1 admin    wheel  34 Jul 19 13:42 Shared -&gt; /Volumes/ExtSSD/shared

Restoring the /Users/Shared directory back to an actual directory — the way it looks as laid down by the macOS Installer — resolves the issue. Now /Users/Shared looks like:
&gt; cd /Users
&gt; ls -l | grep Shared
drwxrwxrwt  25 root      wheel  800 Apr 17 14:17 Shared

With /Users/Shared no longer a symlink, the macOS Catalina install/update process works fully and successfully.