Here's an update on this. We seem to have been able to narrow down the issue to when they are using the DECT headsets (5330 phones) and the call is external.
It fails to give an alert tone ~50% of the time.
Here's how the call comes in:
Call hits Auto Attendant 1st.
Call is then xferred to either an ACD path or direct to an agent.
No Auto Answer Alert tone ~50% of time.
It appears to work just fine if dialing the phones ext internally or if not using the DECT headset so the call is immediately on speaker phone.
Tech support is supposed to be setting this up in the lab to test now.
Ralph