We gave up on trying to run software on the dev machines for VOIP and went with GrandStream GXV-3175's (with asterisk in the middle on a datacenter server). It

We gave up on trying to run software on the dev machines for VOIP and went with GrandStream GXV-3175's (with asterisk in the middle on a datacenter server). It was expensive (like $300 each) but it works better than any software solution we could find, even Facetime.