Opal4 is back online.
The earlier assessment of an external network problem was incorrect, this appears to have been another network attack on Opal4.
The attacks that have taking opal4 down haven't seemed to be particularly massive - similar attacks happen on other shared hosts in our infrastructure and those machines are fine. Because of this we're planning to replace opal4 in the coming weeks. We'll contact all affected customers individually with the details as we finalize the plan.