But only if the handset is returned to the cradle. The caller will hear the on hold music for a second and then the call is dropped. Latest version of 3CX on Azure with Htek phones, no other problems.
This is the default mode the phone works in from this manufacturer. As far as I'm aware this is not configurable when putting the hook back. Only configurable for transfers and conference, but not while on hold.
Strange as this behavior just started around Christmas and we've had the system in place for a year and a half or so. We have a workaround (just don't put the hand set back in the cradle!) the users just have to get used to not doing this - they've hung up on a few customers over the last few days. Thank you John.