We're seeing network instability caused by one of our vendors distribution switches. Engineers are currently working on the issue.
09:33am BST: Firmware issues with the redundant Cisco Nexus 9000 series switches have been worked around and the issue has been escalated to Cisco. Services should now be operating as normal.
09:00am BST 18th April: Firmware replaced with assistance from vendor, stability issues should now be resolved.