sandbox50 dev cluster is now back online. Issue appeared to be network related, due to a problem with a router for this cluster. Data centre switched to a failover router & the network issues has been resolved. This only impacted the sandbox50 dev cluster, no live sites or servers were impacted.
sandbox50 dev cluster is now online, more details shortly.
We're currently investigating an issue with the sandbox50 dev server cluster. Details will be here once we know more.