DPC3925 no CPC signal

[artis9278]

Been using DPC3925 provided by my service provider here in Singapore (Starhub). Have used 3 different telephone brands but still have the same issue: the line remains connected (with busy signal) even after the other party hangs-up already. I suspect the router/modem is not sending the correct disconnect (calling party control) signal to the phone. Appreciate your valuable inputs & advice.

[artis9278]

Update:

Brought my telephone units to my friend, who uses another service provider with different voice modem. My telephone units work perfectly there. So this further confirms the issue is from Cisco DPC3925 router/modem.

Cisco, please check this & provide the fix ASAP!...