Tarbat - with your number 4 on the list, you have:
The Hex Code Confusion Bug - Data (callsigns, altitudes, squawks, etc) being assigned to the wrong aircraft.
Airnav have strongly stated this cannot be fixed. Therefore I think this should be instead called:
The Hex Code Confusion Design Limitation.
All we can hope for in the future is that in the supporting Airnav literature and tutorials fully explain the nature of this limitation, so that users can understand that not every aircraft they see in myflights is actually airborne in reality.