Calibre Server gives error 500 on Stanza/OPDS lists

[mcbastos]

This is new, as of version 2.67.0. I reverted to 2.66.0 and the problem disappeared. Reinstalled 2.67.0 and it came back.

I use Calibre 64-bit version on Windows 10 Pro.

If I use Aldiko on my Android phone to attempt to download a book from Calibre server, the following happens:
1. I can log on the http://x.x.x.x:8080/stanza normally, and see the main menu with the several available listings (By Newest, By Title, By Authors etc.)
2. When I attempt to open one of the listings, I get a "500 Internal Server Error" message.

OPDS listing is similarly affected.

But using either Aldiko or a web browser (Chrome, Firefox) to open the regular Web page of the server (NOT the /stanza or /opds pages), I can see list the books and download them.

Note that I have a rather big catalog -- nearing 1400 books. It may be that the problem won't show itself with small catalogs.