PureEngage On-Premises

Today We find one telephone abnormality,then many calls was disconnected due to this phone.
I want know what kind of abnormal condition will causes error 'Resource busy'.

Without any details from log, is not possible to get you any relevant hint. Try to find out the root-cause within the logs before the EventError is generated or contact your Genesys customer care contact for opening the #SR.

My guess: the agent hit the DND button on the phone.

The Statserver has the extension in WaitForNextCall status but when a call is routed there, it responses with a 486 Busy Here resulting in an EventError. This can repaidly clear a queue as call after call is routed to the phone.

May be a faulty phone that needs to be rebooted, but more likely the DND button was pressed accidently (or on purpose). I don't think there is an easy way to prevent this since this won't trigger NAS. We disable the DND and forwarding buttons on our phones to remove that possibility.