Network validation failed

firstly I have been forwarded here from customer support.
A problem, in which me and Josh (the developer of PPPwidget3) are out of ideas after 5 months, is after properly done dialing and network creation we’re getting this error (from logcat):

D ConnectivityService: NetworkAgentInfo [PPP () - 101] validation failed

Therefore any user of Shield K1 (Android N) is not able to use Google Apps and system parts dependent on an internet connection. PPPwidget3 was working on Android L & M properly. Tablet needs to be rooted to get any internet connection.
Link to the discussion:,
link to the last state