I have never been able to reproduce your problem, and no other users have ever reported it. However, I have added a few more debug statements to help me help you.
Added: Also post a screen print of both your LC Configuration window showing your chosen custom column names, as well as Preferences > Add your own columns so I can see all of the settings for each of the custom columns you are using with LC.
Added: Also post the Calibre error messaged text that you get within the Calibre GUI in addition to the full debug log made concurrently with the error message.
Added: Also get into debug mode directly by running this from a .bat file or a command line:
Code:
"C:\Program Files\Calibre2\calibre-debug.exe" -g
Added: Also manually download and upgrade to the latest version of LC released on 2 July 2020. Since the special testing version was the same, you will not be automatically notified that there is a new release.
DaltonST