I was wondering if you found a solution for the problem you were facing on the ASA 5505 device?
I am facing the same problem and I shared my 'sh tech' output with a friend who was Cisco Certified. She said that the reason why this problem happens is because of the Flash memory is not able to handle a sudden flood of packets which makes the device hang.
The solution for this she suggested is increasing the flash memory or updating the software which i am not able to do. I can't raise a TAC number as well with Cisco.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...