Yellow (pending) thread after resending from SMAT

It may just be that I am too close to a long weekend and my brain has switched to econo-mode, but I am struggling to understand what is going on with one of my processes.

I have an inbound pdl thread from our lab system that gets charges dumped to it nightly. It stays in an opening state because Cerner only opens the connection when it needs it. It has been working for a while just fine for years. Now, I have added a route to a new outbound thread that uses an outbound database protocol to write to an MSSql DB.

When I resend a file to the source thread and limit the route to only the db connection, the message is successfully sent and is written to the database. The problem is that the incoming thread to which I resent the message turns yellow and puts the resent message into a pending state (but it doesn’t show in the recovery database). If I restart the thread, the pending message clears and doesn’t go to the RDB or EDB.

Why is this happening?