Why pfsense traffic graph looses host names frequently?

  • Most of the time I see pfsense traffic graph of our gateway looses host names.

    Wile dns integration is ok as below, ( is our local dns which resolves internal hostames)

    I was wondering have i missed dns entries in the dns server , so i made a general query through my terminal for above two ip's .. They seems to be working fine..

    What could be the problem ?