e_adept_xml_syntax error?

I keep getting the e_adept_xml_syntax error on four out of every five books I try to download from the same source (EBSCO). I run a Macbook Pro (Sierra 10.12.1), and have tried all the solutions suggested for this error that I can find (restart, reinstall, de- and reauthorize, etc.) but so far nothing has helped at all. It's particularly frustrating as some of the books from the same source work perfectly fine. Any suggestions?