Lightning Source is Ingram Digital (a distributor FW uses). I know Ingram is having a bunch of issues with the 'Agency 5', but IIRC folks have been having the problem you mention for a long time now. There was a huge thread around here where this was being discussed, but I can't remember if any solutions were found.
EDIT: Here's the thread I was thinking of. There are some things there folks got to work...
https://www.mobileread.com/forums/showthread.php?t=45206