One minute your instance is humming along just fine, then suddenly it’s spewing strange errors something like
The customized site map could not be used because it is configured incorrectly. The default site map has been applied instead.
To resolve this issue, repair the customized site map and import it again.
The url, as frequently is the case, contains even more bizarre
Error Details: Sub area with id “nav_workflow” has an empty title.
The sandbox copied couple hours prior is humming along just fine, the other users report that they had this issue few minutes ago but everything is unicorns and rainbows right now.
Most likely, there was indeed a temporary issue that has been resolved but now you are stuck with the bad front-end server/process that is dealing with your requests. Quick test: if you can connect in incognito mode then the rotten service-side connection that your session is pegged to (by the application load balancer), is most likely the case.