Thanks for replying, Mr. Kovid Goyal. I'm indeed up to date with Calibre, currently using 4.19 64-bit.
https://imgur.com/7OMFzEL
Perhaps I should try a complete reinstall by removing the configuration directory? I have been just copy-pasting the configuration folder whenever I have to reinstall Windows so it might have been messed up somehow in the process.
If I have to remove everything to do a clean install, would you be so kind as to point me how to back up settings like my virtual libraries and custom columns, etc? I like the current library UI I've refined over the multiple years I've been using this awesome software.