GitLab CI jobs fail to fetch Git: "RPC failed"

Getting source from Git repository 01:02
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/tails/tails/.git/
error: RPC failed; curl 92 HTTP/2 stream 0 was not closed cleanly: PROTOCOL_ERROR (err 1)
fatal: the remote end hung up unexpectedly

See:

• https://gitlab.tails.boum.org/tails/tails/-/pipelines/2790
• https://gitlab.tails.boum.org/tails/tails/-/pipelines/2789
• https://gitlab.tails.boum.org/tails/tails/-/pipelines/2788
• https://gitlab.tails.boum.org/tails/tails/-/pipelines/2787
• https://gitlab.tails.boum.org/tails/tails/-/jobs/19754
• https://gitlab.tails.boum.org/tails/tails/-/pipelines/2810
• https://gitlab.tails.boum.org/tails/tails/-/pipelines/2813

We need to try to isolate the problem and make it reproducible, and try to determine which side is terminating the HTTP/2 stream.