We disabled the Heroku feature which was causing the problem, and have been monitoring since. As there doesn't appear to be any lingering effects we think this problem is resolved.
We use Heroku as our hosting provider, so if they have a problem, we have a problem. Currently liasing with them to get to a solution.
Posted Nov 21, 2017 - 15:18 UTC
Investigating
This appears to be a problem with our hosting provider. We are speaking with them with the highest urgency, and will update here when we have more information.