I know there isn't any suggestion and I don't expect any as that happened only once in my 1 year flying timeline (my logbook says allmost 250 flying hours) with my F550, so I treat this as a random case. Just for DJIs debbug team.

I am experiencing exactly the same problem.  I have updated all firmware and replaced all hard wire connections.  The problem is intermittent.  I am glad to hear it is not just me!

I wonder though....for the "poor" of us who don't have Phantoms or Inspires or super duper Zenmuses....is any debugg team here?....