Problems Dialing numbers with Automated Attendants

We have users that are having random trouble dialing numbers with automated attendants. Once dialed the attendant does not recognize the digits being entered in by the end user. Some systems work fine but others do not accept any keys entered.

Is this dialing over Zap channels or SIP channels? If SIP, try changing the dtmfmode to something else to see if it resolves the issue. For Example, if you are using ulaw, try changing the dtmfmode to inband from rfc2833.

SIP Channels and ulaw, we have tried changing the dtmfmode but the problem still persists.