Salsa HTTP requests randomly get terminated on HTTP/2 protocol errors or HTTPS issues without returning any responses

This is visible to users with UI notifications such as:

We are currently unable to fetch data for the pipeline header.

Looking at the browser console, this was a HTTP request to https://salsa.debian.org/api/graphql?query=query%20getPipelineHeaderData(.. which failed on net::ERR_HTTP2_PROTOCOL_ERROR:

Occasionally in CI jobs I also see this error:

When it happens the dev console shows the same HTTP/2 issue:

Any idea where these might stem from? Does salsa.debian.org (godard.debian.org) have some reverse proxies or HTTP/2 or HTTPS termination hosts in front of GitLab?

changed the description

This still happens, but rarely: