Cogent to Comcast IPv6 broken?

[will at loopfree.net (Will Orton)]

Cogent from various west coast USA locations seems to have trouble getting to some Comcast ipv6 addresses:

Cogent LG Los Angeles to www.comcast6.net
traceroute to 2001:558:fe16:7:69:252:216:215 (2001:558:fe16:7:69:252:216:215), 30 hops max, 80 byte packets
 1  2001:550:1:317::1 (2001:550:1:317::1)  70.184 ms  70.181 ms
 2  * *
 3  * *
 4  2001:550:4::51 (2001:550:4::51)  15.013 ms  14.981 ms
 5  * *
 6  * *
[ ... ]


Cogent LG San Francisco ipv6 trace to www.comcast6.net
 traceroute to 2001:558:fe16:7:69:252:216:215 (2001:558:fe16:7:69:252:216:215), 30 hops max, 80 byte packets
 1  2001:550:1:31f::1 (2001:550:1:31f::1)  0.367 ms  0.369 ms
 2  * *
 3  * *
 4  * *
[ ... ]

Cogent LG San Jose ipv6 ping to www.comcast6.net
PING 2001:558:fe16:7:69:252:216:215(2001:558:fe16:7:69:252:216:215) 56 data bytes

--- 2001:558:fe16:7:69:252:216:215 ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 13999ms


Cogent LG San Jose ipv6 ping to speedtest.comcast.net (Los Angeles does same thing, but Kansas City works):
PING 2001:558:fe2a:3:69:241:64:6(2001:558:fe2a:3:69:241:64:6) 56 data bytes

--- 2001:558:fe2a:3:69:241:64:6 ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 14000ms

from Los Angeles same thing, but from Cogent's LG Kansas City it works:
PING 2001:558:fe2a:3:69:241:64:6(2001:558:fe2a:3:69:241:64:6) 56 data bytes
64 bytes from 2001:558:fe2a:3:69:241:64:6: icmp_seq=1 ttl=55 time=35.6 ms
64 bytes from 2001:558:fe2a:3:69:241:64:6: icmp_seq=2 ttl=55 time=35.7 ms
64 bytes from 2001:558:fe2a:3:69:241:64:6: icmp_seq=3 ttl=55 time=35.6 ms
64 bytes from 2001:558:fe2a:3:69:241:64:6: icmp_seq=4 ttl=55 time=35.6 ms
64 bytes from 2001:558:fe2a:3:69:241:64:6: icmp_seq=5 ttl=55 time=35.6 ms

--- 2001:558:fe2a:3:69:241:64:6 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4043ms
rtt min/avg/max/mdev = 35.620/35.676/35.734/0.241 ms


This is similar to issues I see with a Cogent IPv6/BGP-enabled transit connection in Los Angeles to a random
Comcast customer address (that is otherwise up and reachable from HE.net, NTT, etc):

(from router with ipv6 BGP Cogent transit connection):
traceroute6 to 2601:7:1300:3d2::1 (2601:7:1300:3d2::1) from 2001:550:2:18::5:2, 64 hops max, 12 byte packets
 1  2001:550:2:18::5:1 (2001:550:2:18::5:1)  1.903 ms  1.120 ms  10.771 ms
 2  * * *
 3  * 2001:550::57 (2001:550::57)  15.654 ms *
     MPLS Label=19852 CoS=2 TTL=255 S=0
     MPLS Label=19207 CoS=2 TTL=255 S=1
 4  * * *


I have Cogent ticket #HD0000005706297  on that but I'm being ignored.
I see the similar things from Cogent IP6 transit out of San Jose.

Anyone at Cogent able to look at this? I basically blackhole big chunks of Comcast ipv6 on my network when I 
enable ipv6 to Cogent.


-Will