A customer has an 824 DS with DR5.

The lines are set to Supervised.

However, if you call into the VM system (startalk flash - possibly a mini),
and hang up, the line stays engaged until the time out transfer to the receptionist occures.

I thought you needed DR5 DS to go with the DS KSU, but my vendor is telling me that this is true only for the older 616 systems.

Is this correct?

If so, what could be the cause if the lines are set to be supervised?

Does the problem occur every time you hang up while in the voicemail? Is it possible that a call is being forwarded to the Startalk at the same time the line is being disconnected? I had a problem once where telco forwarding to VM was set to 4 rings and one of the sets was FNA 4 rings to the Startalk. The mailbox in question kept getting messages with a telco recording or a reorder tone.