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This doesn't look like a fatal error, but like an incomplete html output in case of reachability issue. Should indeed be handled better.
forge.joomlapolis.com/issues/8922

We did a planed offline full upgrade this morning of our redundant cluster, that was needed ultra-exceptionally with a short downtime. Normally our downtimes are measured in miliseconds or in seconds at most, thanks to the fully redundant hosting infrastructure. Sorry about the interruption of service. But your point is valid, and we will handle it.