I am updated koha installation from 3.8 -3.10.02 using debian packages. But when i run process message queue.pl script after fines.pl and overdue_notices.pl it send the message without body of the message. Subject line and sent address are ok but the body is disappeared from the message. But patron pages lists all notices regularly with the content of the body.
When I was working on a fix 8378, which might have not made it out, I noticed that the body might have not been UTF8 encoded as we do in other places in the code before we persist a string. If certain unencoded characters are in the body, MYSQL will silently truncate from that point onward in the string when saved. So that might help someone investigating. You could look at bug 8378 to see about how/where I encoded the notice. You can verify by selecting your published notice from the message queue to see if its persisted. In my case currency for the fine was causeing truncation from that point onward.
Overdue notices are working correctly in current versions of Koha (recently tested).