Web Appliance Intermittent 'Lock Ups'

Is anyone else experiencing issues with this appliance firmware level?

Intermittently and randomly the appliance (now appliances as we have deployed a 2nd and soon to be 3rd on alternative hardware and internet breakouts) the device refuses to pass traffic.  No network issues, GUI remains responsive.  DNS checks pass.  Direct browsing via the upstream firewall is successful, a 2nd appliance using the same upstream firewall for connectivity continues to function.

Looks to be some kind of bug with the appliance.  2-3 weeks into a case with Sophos and unresolved.

Has anyone experienced this kind of issue or lock up?