For the past couple of months, I've started receiving reports of occasional call drops, always at the 15 minute mark.

We play around with the usual... port forwarding, disabling sip alg, setting "nat=yes" in the client device.

Nothing seems to permanently fix the issue. It seems to come and go. A number that worked for years, will suddenly start dropping at 15 minute mark. Then the next day it works fine.

Anyone else have this problem.

Any ideas or suggestions?