Couchbase 6.0.2 crashes multiple times

Hi everybody
We had this strange behavior with couchbase 6.0.2 build 2413
I don’t really know the reason but couchbase server crashes couple times and we have no idea about the reason.
I am going to attach the all the log files. I will move soon to CB 6.5.0 at least, but before to do that I would like to have your opinion.
Thanks for any help

Logs files are too big, so I am linking here the file.

Can you share the more information? Is couchbase server crashing during the CB services start and are you seeing any crash dump inside var/lib/couchbase ?

No CB was running and the we got the crash, from our application we saw it can connect to the CB when suddenly it become unreachable. We look to the log and we saw the CB was crashed, the 8091 was not responding anymore. It happens couple weeks ago, and we rebooted the machine after few days it happens again, so we rebooted again the machine and I sent all the logs contained the /opt/couchbase/var/lb/couchbase/logs
It happens at last 3 times during last 2 weeks.

FYI Saturday (2 days ago) we had another crash and we decided to migrate on the fly on cb 6.5.1 and sync_gateway 2.7.3, unfortunately I could get the log of the last crash.

Thanks for any help.