[2.4b5] push sometimes fails with "missing referenced chk root keys"

After installing bzr 2.4b5 from the beta ppa, I noticed that the next push for all my usual development branches was taking ages.
I was told on IRC that this was due to the upload of missing tagged revisions, and indeed I have hundreds of tags on most of my branches, due to our QA system automatically tagging commits. (This is not directly related to the crash as far as I can see, but could be helpful during analysis).

So, I was now trying to push revision [1] using 2.4b5 and it crashed with the following traceback:

   File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 131, in run
     self.cleanups, self.func, self, *args, **kwargs)
   File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 165, in _do_with_cleanups
     result = func(*args, **kwargs)
   File "/usr/lib/python2.7/dist-packages/bzrlib/branch.py", line 3441, in _push_with_bound_branches
     result = self._basic_push(overwrite, stop_revision)
   File "/usr/lib/python2.7/dist-packages/bzrlib/branch.py", line 3403, in _basic_push
     graph=graph)
   File "/usr/lib/python2.7/dist-packages/bzrlib/decorators.py", line 217, in write_locked
     result = unbound(self, *args, **kwargs)
   File "/usr/lib/python2.7/dist-packages/bzrlib/branch.py", line 3313, in _update_revisions
     self.fetch(stop_revision=stop_revision)
   File "/usr/lib/python2.7/dist-packages/bzrlib/decorators.py", line 217, in write_locked
     result = unbound(self, *args, **kwargs)
   File "/usr/lib/python2.7/dist-packages/bzrlib/branch.py", line 3290, in fetch
     fetch_spec=fetch_spec)
   File "/usr/lib/python2.7/dist-packages/bzrlib/remote.py", line 1656, in fetch
     find_ghosts=find_ghosts, fetch_spec=fetch_spec)
   File "/usr/lib/python2.7/dist-packages/bzrlib/decorators.py", line 217, in write_locked
     result = unbound(self, *args, **kwargs)
   File "/usr/lib/python2.7/dist-packages/bzrlib/vf_repository.py", line 2497, in fetch
     find_ghosts=find_ghosts)
   File "/usr/lib/python2.7/dist-packages/bzrlib/fetch.py", line 75, in __init__
     self.__fetch()
   File "/usr/lib/python2.7/dist-packages/bzrlib/fetch.py", line 102, in __fetch
     self._fetch_everything_for_search(search_result)
   File "/usr/lib/python2.7/dist-packages/bzrlib/fetch.py", line 130, in _fetch_everything_for_search
     stream, from_format, [])
   File "/usr/lib/python2.7/dist-packages/bzrlib/remote.py", line 2109, in insert_stream
     (verb, path, resume_tokens) + lock_args, byte_stream)
   File "/usr/lib/python2.7/dist-packages/bzrlib/smart/client.py", line 181, in call_with_body_stream
     expect_response_body=False)
   File "/usr/lib/python2.7/dist-packages/bzrlib/smart/client.py", line 81, in _call_and_read_response
     expect_body=expect_response_body),
   File "/usr/lib/python2.7/dist-packages/bzrlib/smart/message.py", line 306, in read_response_tuple
     _raise_smart_server_error(self.args)
   File "/usr/lib/python2.7/dist-packages/bzrlib/smart/message.py", line 351, in _raise_smart_server_error
     raise errors.ErrorFromSmartServer(error_tuple)
 ErrorFromSmartServer: Error received from smart server: ('error', "Internal check failed: Cannot add revision(s) to repository: missing referenced chk root keys: [StaticTuple('sha1:32b5964d29924e611fc4b50e92ca0aeed58c2cea',)]")

I don't know if this is related to the large number of tags I have on that branch:
  $ bzr tags | wc -l
  1084
  $ bzr tags | grep '?' | wc -l
  952

This looks like an issue of 2.4, because after downgrading bzr and bzrlib to version 2.3.1-1ubuntu1, the push went just fine.
I did manage to push with 2.4b5 on some of our other branches (with hundreds of tags), though it took a long time.

See the attached crashlog, and feel free to request any other useful info I could provide.

Thanks!

[1] rev 3513 revid: <email address hidden> on lp:~openerp/openobject-server/trunk