I appreciate the feedback and find it interesting that other users of iFly have had similar experiences. I occasionally had brief NMEA dropouts with the 700 and Trio but after discussing this with the Trio guys we decided the very tight integrity filters in the Trio device was rejecting a random incomplete or faulty sentence. After the Trio sees several good data sentences it restores the NMEA handshake.
But it got more interesting when I connected the Dynon to the same 720 NMEA feed. When the Trio rejects data the Dynon continues to display NMEA data. But what I'm seeing now is *both* devices going down simultaneously and the iFly deleting NMEA from the settings page.
Since the problem is intermittent and always shows an absence of NMEA being ported when looking at the iFly settings during a failure, I still am inclined to believe the problem resides in the Win tablet firmware but I have been unable to determine a pattern or trigger for the failures. However....to eliminate one possibility I will replace the adapter cable. I have used the same USB/serial data adapter since first flying the 700 several years ago and it has no physical damage....but maybe the chip has gotten flakey.
Thanks again for the feedback!