This symptom may be observed when hairpinned calls are placed with a Cisco 3725/3745/2691 gateway with AIM-ATM-VOICE-30 module installed and running Cisco IOS version 12.2(15)ZJ03 or 12.3(07)T.
You can verify that the symptom occurs through the output of the show connection all EXEC command.
The command output shows one timeslot twice and shows that it is connected to both another timeslot and to a Digital Signal Processor (DSP) DSP resource.
The command output indicated shows a timeslot 1 connected to timeslot 23 (22) as well as DSP 07/00/00. There should be a single timeslot-to-timeslot or DSP connection, but not to both at the same time, as shown:
2691# show connection all ID Name Segment 1 Segment 2 State