Not sure what the problem might be. It is worth checking that for the books that show problems you actually have the book in one of the Included Formats you have listed in calibre2opds on the Advanced Customisation Options tab. If you are using Aldiko also check that you have Aldiko compatibility set.
Assuming that the above does not show up a specific problem then it could well be something to do with the CYRILIC character encoding. I am reasonably certain that will never have been explicitly tested. Could you then consider raising a bug on the
calibre2opds Project Page? It would be useful if you could attach the following to the bug report:
- At least one of the book.xml files from the book folder in the generated catalog so that we can check if there is any download link inside the file at all.
- The log from the last generation run. If nothing else this will show what generation time options you used.
- If it is not too sensitive, the calibre metadata.db file so we can try and recreate the problem using your database. Ideally mention the names of some books exhibiting the issue.