The only time a lock file is generated is when the document itself is opened. Your book file should always point to the same document, so conflicting copies sounds like either you have multiple .indb files pointing to multiple copies of the documents, or users are saving copies that are not included in the .indb.
We're using the same book file, maybe we're not saving correctly. Would a conflicting file occur if they open the file, make changes, close it and then not save the book?
I wouldn't think so, but it's important to save the book too.