Another broken SMSC DLR implementation?

Before I start ranting, this is a question - and not a statement, so please don't flame me if I'm wrong! :-)

If you have multiple SMPP connections to a provider, shouldn't the DLRs come back on the connection that the message was sent out on? We're having an issue with one of our providers that DLRs are coming back on the wrong SMPP connection, so Kannel is ignoring them.

The only way I've found of fixing it so far is disabling the other three connections, so the only way they can return the DLRs is through the originating connection. 

Any suggestions? 

Alex