Calls fail to occupied extension

Hello, we are having an odd issue with one extension.
When the extension is occupied by an inbound, outbound, internal, external or queue calls any additional inbound calls are rejected and the calling phone reports “Call Failed”.
Call waiting is enabled on the extension.

Is CF busy enabled? What does the log say when one of these failures occurs?

CF Busy is not enabled, I can post full log but this seems related:

-- Executing [[email protected]:49] ExecIf("SIP/100-00001118", "0?Set(DIALSTA                                                                                        TUS=NOANSWER)") in new stack
-- Executing [[email protected]:50] NoOp("SIP/100-00001118", "Returned from d                                                                                        ial-one with nothing to call and DIALSTATUS: BUSY") in new stack

Looks like toggling CW off and then on again resolved the issue, possible quirk in the DB?