This is happening on multiple 3CX phone systems using service pack 2 and 3, with multiple VOIP providers. We have perfect audio inbound and outbound, but when send calls Forward to Outside number they are failing about 30-50% of the time. We have this issue in San Antonio, TX and have this with Spectrum also know as Charter and NexVortex. It seems that when we forward to certain numbers... we get a failure about 30-50% of the time. If we forward to a certain "good" numbers. we never get a failure. We have eliminated it being a cell phone vs land (analog) line, long distance vs local, also its not confined to a certain carrier either. We are at a loss and can't see to get this resolved. Any help would be greatly appreciated.