G root pmtu?

it seems that G root ops are blocking dns ops mail servers. the more i
think about that the sicker i think some folk out there are. but
anyway, anyone else seeing this kind of problem with g root?

http://dnsviz.net/d/gn/dnssec/ whines

    gn/DS (alg 8, id 38486): No response was received until the UDP
    payload size was decreased, indicating that the server might be
    attempting to send a payload that exceeds the path maximum
    transmission unit (PMTU) size. (2001:500:12::d0d,