DNS format error

[Yang Yu]

I spotted DNS format error in bind 9.9.5 log

queries
28-Jul-2015 23:19:27.198 client client_IP #50270 (www.icann.org):
query: www.icann.org IN AAAA + (client_IP)
28-Jul-2015 23:19:29.872 client client_IP #46483 (www.icann.org):
query: www.icann.org IN A + (client_IP)


resolver
28-Jul-2015 23:19:35.621 DNS format error from 192.0.32.252#53
resolving www.vip.icann.org/DS: inval
id response
28-Jul-2015 23:19:35.789 DNS format error from 192.0.36.252#53
resolving www.vip.icann.org/DS: inval
id response
28-Jul-2015 23:19:36.022 DNS format error from 192.0.47.252#53
resolving www.vip.icann.org/DS: inval
id response

I am unable to replicate this issue with dig www.icann.org. What could
have bind received that resulted in DNS format error in this
particular case?

Yang