Symptom
This is an enhancement request for the error message:
ARP-3-INVAL_HDR_HRD_TYPE arp [4716] Found incorrect hardware type in ARP header: 6
It would be easy if the error message would contain the MAC address.
Workaround
Use ethanalyzer to determine the source of the packets:
ethanalyzer local interface inband display-filter "arp.hw.type == 6" limit-captured-frames 100000