Read/Unread Marks are not consistent.

I periodically observe that Windows Mail fails to maintain Read / Unread
Marks consistently. In one scenario I opened and read and email from my
Inbox. I then replied to the email and closed it. Back in the Inbox view
the message is still marked as Unread despite my having clearly read and
replied to it.

In another scenario I open and read an email in one folder. I then copy the
message to another folder. Sometimes it stays marked as read in the
destination folder, sometimes it gets changed to unread. I can't identify
any variable to make it predictable.

Both of these scenarios are under IMAP mail. Has anyone else experienced
this? Are there any solutions?