We have several sites all recently moved to a hosted broadworks PBX solution provided by Hostcomm.
All sites use netgear POE switches and Yealink T26P handsets, with Draytek 2830 routers.
We experience a delay when incoming callers ring in, the operator answers and cannot hear the caller speak for approximately 10 seconds.
Sometimes it works sometimes it doesnt, approx 50% of the time the call is fine.
We have spoken with Hostcomm who have told us it is a local issue, perhaps bandwidth, but the sites are on fibre and speedtests show there is plenty of available bandwidth, Draytek have talked us through enabling / disabling SIP ALG on the router (no difference), extending the UDP portmap time with the command portmaptime -u 86400, updating the firmware and adding STUN servers - again no difference.
Any help would be greatfully accepted - this is a serious issue.