Zero mac in ARP list ?

RouterOS Beginner Basics
2

ROS version?

I have seen smiiliar topics so maybe possible bug
http://forum.mikrotik.com/t/help-how-to-protect-router-automatic-mac-generate/94593/1
http://forum.mikrotik.com/t/router-rb450-and-750-mac-000000-00/94901/1