This is a tricky one. As it's not a high frequency failure I think we can do first some enhanced logging, such as logging with WARN level untimely context switch and where they happen.
This bug is > 365 days without activity. We are unsetting assignee and milestone and setting status to Incomplete in order to allow its expiry in 60 days.
If the bug is still valid, then update the bug status.
I confirm this is a different case from the one that we're already aware of, affecting VIP operations as well: https:/ /bugs.launchpad .net/neutron/ +bug/1313794