ApplyDeltaError: Unexpected source buffer size when force pushing a branch

In my workflow on Github, I use to force-push PR branches a lot before finally integrating them.

For some time now I randomly hit dulwich.errors.ApplyDeltaError: Unexpected source buffer size when trying to force push a branch. I am not able to consistently generate a repo which hits the error, even because this happens in the middle of a heavy programming session, and at that time I am worried about not losing data.

My current dulwich version is dulwich==0.20.33, mercurial 6.1, hg-git d931a1ee7e0c. Anyway, this happened even with older versions of each component.

$ hg push --bookmark some-name --force
pushing to git+ssh://git@github.com:myorg/myrepo.git
** unknown exception encountered, please report by visiting
** https://mercurial-scm.org/wiki/BugTracker
** Python 3.9.7 (default, Sep 10 2021, 14:59:43) [GCC 11.2.0]
** Mercurial Distributed SCM (version 6.1+hg2.1ceca11e6546local20220304)
** Extensions loaded: amend, churn, extdiff, hggit 0.10.4 (dulwich 0.20.33), histedit, mq, patchbomb, rebase, show, strip, uncommit
Traceback (most recent call last):
  File "/usr/bin/hg", line 61, in <module>
    dispatch.run()
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 144, in run
    status = dispatch(req)
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 250, in dispatch
    status = _rundispatch(req)
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 294, in _rundispatch
    ret = _runcatch(req) or 0
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 470, in _runcatch
    return _callcatch(ui, _runcatchfunc)
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 480, in _callcatch
    return scmutil.callcatch(ui, func)
  File "/usr/lib/python3/dist-packages/mercurial/scmutil.py", line 153, in callcatch
    return func()
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 460, in _runcatchfunc
    return _dispatch(req)
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 1273, in _dispatch
    return runcommand(
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 918, in runcommand
    ret = _runcommand(ui, options, cmd, d)
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 1285, in _runcommand
    return cmdfunc()
  File "/usr/lib/python3/dist-packages/mercurial/dispatch.py", line 1271, in <lambda>
    d = lambda: util.checksignature(func)(ui, *args, **strcmdopt)
  File "/usr/lib/python3/dist-packages/mercurial/util.py", line 1887, in check
    return func(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/mercurial/util.py", line 1887, in check
    return func(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/hgext/mq.py", line 4239, in mqcommand
    return orig(ui, repo, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/mercurial/util.py", line 1887, in check
    return func(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/mercurial/commands.py", line 5787, in push
    pushop = exchange.push(
  File "<base>/hg-git/hggit/util.py", line 63, in inner
    return f(*args, **kwargs)
  File "<base>/hg-git/hggit/__init__.py", line 592, in exchangepush
    pushop.cgresult = repo.githandler.push(remote.path, revs, force)
  File "<base>/hg-git/hggit/git_handler.py", line 438, in push
    self.export_commits()
  File "<base>/hg-git/hggit/git_handler.py", line 385, in export_commits
    self.export_git_objects()
  File "<base>/hg-git/hggit/git_handler.py", line 564, in export_git_objects
    self.export_hg_commit(ctx.node(), exporter)
  File "<base>/hg-git/hggit/git_handler.py", line 631, in export_hg_commit
    commit.message, extra = self.get_git_message_and_extra(ctx)
  File "<base>/hg-git/hggit/git_handler.py", line 759, in get_git_message_and_extra
    message = b"".join(apply_delta(message, extra[b'message']))
dulwich.errors.ApplyDeltaError: Unexpected source buffer size: 430 vs 100

• is hg-git feeding bad data to dulwich?
• is dulwich at fault instead?
• is it possible that the .hg/git portion of the repo became corrupted?