Key error pulling from GitHub

(there was as similar issue #49 (closed) but this was closed nine years ago)

Latest hg-git: pulling from GitHub via https or ssh fails (pushing works fine):

hg pull git+ssh://git@github.com/thorstenkampe/dev
pulling from git+ssh://git@github.com/thorstenkampe/dev
** unknown exception encountered, please report by visiting
** https://mercurial-scm.org/wiki/BugTracker
** Python 3.9.6 (default, Jul 24 2021, 23:35:14) [MSC v.1929 64 bit (AMD64)]
** Mercurial Distributed SCM (version 6.0+hg12.5c4180091fe8)
** Extensions loaded: extdiff, hggit unknown (dulwich 0.20.6)
Traceback (most recent call last):
  File "<string>", line 40, in <module>
  File "mercurial.dispatch", line 144, in run
  File "mercurial.dispatch", line 250, in dispatch
  File "mercurial.dispatch", line 294, in _rundispatch
  File "mercurial.dispatch", line 470, in _runcatch
  File "mercurial.dispatch", line 480, in _callcatch
  File "mercurial.scmutil", line 153, in callcatch
  File "mercurial.dispatch", line 460, in _runcatchfunc
  File "mercurial.dispatch", line 1273, in _dispatch
  File "mercurial.dispatch", line 918, in runcommand
  File "mercurial.dispatch", line 1285, in _runcommand
  File "mercurial.dispatch", line 1271, in <lambda>
  File "mercurial.util", line 1888, in check
  File "mercurial.commands", line 5456, in pull
  File "F:\scoop/persist/mercurial\hggit\util.py", line 74, in inner
    return f(*args, **kwargs)
  File "F:\scoop/persist/mercurial\hggit\gitrepo.py", line 197, in exchangepull
    pullop.cgresult = repo.githandler.fetch(remote, heads)
  File "F:\scoop/persist/mercurial\hggit\git_handler.py", line 339, in fetch
    result = self.fetch_pack(remote.path, heads)
  File "F:\scoop/persist/mercurial\hggit\git_handler.py", line 1374, in fetch_pack
    ret = self._call_client(remote, 'fetch_pack', determine_wants,
  File "F:\scoop/persist/mercurial\hggit\git_handler.py", line 1411, in _call_client
    return func(path, *args, **kwargs)
  File "dulwich.client", line 933, in fetch_pack
  File "dulwich.client", line 695, in _handle_upload_pack_head
  File "dulwich.object_store", line 1299, in next
  File "dulwich.repo", line 315, in get_parents
  File "dulwich.object_store", line 121, in __getitem__
  File "dulwich.object_store", line 506, in get_raw
KeyError: b'50a819b37ec5c68a106c56c5881106cbaecd7e63'