Yeah I'm noticing the same thing with my he.net tunnel:
I'm wondering what could be causing this - how could a HE.NET tunnel not be reachable by another HE.NET tunnel, but is reachable via other services?
descr: XS News BV
status: ASSIGNED PI
source: RIPE # Filtered
aren't you pining away every day doing whois's etc to increase your sage score?
this netblock is not HEs, and is not a tunnel.
Probably a broken peering somewhere, the v6-backbone is sufferring from reachability issues like any growing network.