The ringback tone is discontinuous and unclear

Hi dear,
according to your description, I think the cause of the symptom is that the timer of the BDC server is abnormal, generally, the fault is caused by NTP time synchronization, if which is the root cause, you need to cancel the NTP time synchronization and then restart the server where the BDC is located.

Of course, to handle this issue, first you need to collect some information such as using tcpdump tool to catch packet on the BDC server, then use the Wireshark tool to filter out the ringback tones and check whether the interval for sending ring back tone RTP packets is 20 ms. If the interval of the RTP packets of each two ringback tone is greater than 20 ms, the playing of the audio ringback tone is abnormal.