It still appears to me this is a timing issue. Below are various things to try.
You will find "DTMF Digit Duration/Pause"
- The default is at 60 milliseconds.
- Try setting this to 80 ms. If it still does not work try 100 ms.
There are several factors at work when a CO Hook flash is performed while on a call, the system essentially reinitializes all call structures. The system does not know why the hook flash was performed, so it assumed it is a re-seize. The person performing the hook flash, is then prompted to enter an outside number.
The timer that is used next depends on whether or not the trunk is "subject-to-toll-restriction". If the "subject-to toll-restriction" flag is enabled, the system checks to see if any digits have been dialed. First, the "Dial Initiation" timer is started. If a digit has been dialed, the total number of digits dialed is analyzed, then either the "Interdigit long" timer (if the number is incomplete per North American Number Plan) or the "Interdigit short" is followed if the telephone number is considered complete.
If the trunk group is NOT subject-to-toll-restriction, the "Interdigit short" timer is always used. Once any one of the dial timers expires (Initiation, Short, or Long interdigit), the system checks for toll restriction. If the call is DENIED, we drop the call. If the call is allowed (i.e. not subject to toll restrict), CO audio is cut through.
Finally, the system will not allow the call to be placed on hold if dialing is incomplete. This is done because call cost must be applied to a call before it can be placed on hold. Since call cost cannot be applied until dialing is completed, one of the dial timers must expire (Initiation, Short, or Long interdigit) to complete dialing. Once one of the dial timers expire, dialing is completed, then call can be placed on hold. When a call is placed on hold, it is valid right away, then call cost calculation begins.
Incoming calls are normally valid immediately upon answer!