I think I answered my own question. My home internet is telephone based ethernet and office is cable internet. This morning, at office, I tried same thing.
Yate accepted incoming calls and did not hang up. "Ringer" in options must be "Off" to avoid sound card error.
sflphone still hung up after less than a minute.
linphone did not hang up (but as mentioned, lack of a decent local address function is a fatal error for my purposes).
And good old Twinkle continued to work as intended (but too cumbersome for my use).
So, at this writing, at least, I think YATE is the only decent gui based sip phone that works perfectly on my VL system. We have hata_ph to thank and I do thank him.
I will continue using Yate, conference calls etc and report back if any problems. Remember, on my system at least, Ringer in preferences must be off for Yate to accept incoming calls.
I don't know why I am having trouble with incoming Yate calls on my home internet but I seriously doubt that is Yate's problem.
BTW, calls to my diamondcard.us sip number and my google-talk number both ring through to Yate.