After hangup, phone rings again...?

When A calls B and then the phones are hung up, B receives a ghost call from A with no one on the line. What causes this? Do I need to do Hangup() calls in my dialplan or something?

What technology? What type of phone? If the technology is SIP, what does sip set debug and/or sip set history show. If dahdi/zaptel, what sort of card are you using?

Which version of Asterisk? Which OS? Which hardware?

etc. etc.

I have been trying to catch this in action, but it doesn’t happen all the time.

Asterisk, Fedora 11, SuperMicro VOIP server

Using SIP with and a gateway VOIP device.

Grandstream GXP-280