Starting last Wednesday, 2020-06-10, the number of connection failures with the Termbox SSR services seems to sharply rise to about 300 - 450 per hour.
The error message is given as:
Wikibase\View\Termbox\Renderer\TermboxRemoteRenderer: encountered a bad response from the remote renderer
with the content being:
upstream connect error or disconnect/reset before headers. reset reason: connection termination
It is currently unclear what is going on or what the effects are. At the very least there is lots of logspam that started recently.