Connect a PC to the serial console of the Pix and let it log all console output to a file. When it crashes again, check the console output at the time of the crash; even if no crashinfo is written to flash, it should be written to console (or at least something should be - if not then it could be a power failure).
When did it start? Was there any change in traffic pattern/traffic type (e.g. did you just start using VoIP - just an example)?
Is this firewall handling a different kind of traffic than the other ones that don't crash?
It could also be a hardware failure - one way to check would be to swap a working FW with the crashing one (and swap the configs as well obviously) - if the same physical unit keeps crashing it's likely a hardware issue. If the swapped one starts crashing it's a bug.
One other thing, if you have download access on cisco.com, I would suggest getting the latest 6.3.5.x software version available - if this is a software bug then there's a chance it's fixed in the newer release.
Login to the FXOS chassis manager.
Direct your browser to https://hostname/, and log-in using the user-name and password.
Go to Help > About and check the current version:
Check the current version availa...
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...