calibre-server crashing after adding custom column like #genre

[hi_caliber]

I was setting up genres as per the manual in my Mac. The latest version I could use on the Mac was 6. I had set-up a Debian LXC to be my calibre-server running the latest version 7.26.
As soon as I had finished setting up the #genre column, caliber-server was throwing tantrums like not finding the library and others.
After about a day of troubleshooting it turns out that editing the database in one version and expecting to work in a later version will lead to problems.
So for anyone who may bump into this issue in the future, make sure that you are consistent as far the Calibre version is concerned across all your 'toys'... :-)