Facetime Drops Calls on Mac

First, FT intermittently works. I plug my iPhone 6S latest version into my Mac HS latest version via USB but it's also on the same WIFI network and sometimes they connect and I can place and receive calls, and sometimes not. When "not" then I have to restart my iPhone and everything works as expected - place outgoing calls on iPhone via screen on Mac, etc.

But no matter what, once I have placed a call, in about 2-5 minutes it's going to drop off. Multiple numbers, not the same but any call at any time of day or night, and WIFI is solid as a rock - testing it using IPMONITORX which shows me any dropouts or delays. I replace calls multiple times and then finally switch to landline because it won't stop dropping. Consistent and reliable problem presentation.