Yes, I'm also seeing the same error quite a lot. For example:

Error 503 Backend unavailable, connection timeout
Backend unavailable, connection timeout

Error 54113
Details: cache-mel11252-MEL 1778815557 3830543164

Varnish cache server
[download]

Update: got this similar one when voting on a node:

Error 503 Resource temporarily unavailable
Resource temporarily unavailable

Error 54113
Details: cache-mel11279-MEL 1778820406 2833676408

Varnish cache server
[download]

Update: another similar one:

Error 503 first byte timeout
first byte timeout

Error 54113
Details: cache-mel11226-MEL 1778826805 3169835228

Varnish cache server
[download]

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