Error 400 "Unsupported protocol version"

We’re capturing minidumps and uploading them to using crashpad. We set an annotation in crashpad for the version, it looks like this:


This has been working well in production for a few months, until we realised that new events stopped arriving in a few days ago. I debug the issue and see that crashpad can’t upload the minidumps. Fiddler shows me this:

HTTP/1.1 400 Bad Request
Server: nginx
Date: Tue, 18 Feb 2020 23:05:27 GMT
Content-Type: application/json
Content-Length: 46
Connection: keep-alive
access-control-expose-headers: retry-after, x-sentry-error
vary: Origin
x-envoy-upstream-service-time: 5
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
{“detail”:“unsupported protocol version (20)”}

The response leads me to believe there is an issue with the version annotation. The request URL looks like this (obfuscated):


This worked for several months and suddenly started failing. Anyone know what’s going on?