Basically I'm having [this](https://lists.mailman3.org/archives/list/mailman-users@mailman3.org/thread/6PLIYZHUOFTOISGRIECI5FFSHMXMV7X5/) exact issue. Sometimes when a message is sent to one of the mailinglists, the message gets shunted and I see the following error in the mailmanlog. ```Dec 30 15:48:26 2019 (2204) Uncaught runner exception: Multiple rows were found for one_or_none() Dec 30 15:48:26 2019 (2204) Traceback (most recent call last): File "/usr/local/lib/python3.6/site-packages/mailman/core/runner.py", line 173, in _one_iteration self._process_one_file(msg, msgdata) File "/usr/local/lib/python3.6/site-packages/mailman/core/runner.py", line 266, in _process_one_file keepqueued = self._dispose(mlist, msg, msgdata) File "/usr/local/lib/python3.6/site-packages/mailman/runners/outgoing.py", line 93, in _dispose self._func(mlist, msg, msgdata) File "/usr/local/lib/python3.6/site-packages/mailman/mta/deliver.py", line 86, in deliver refused = agent.deliver(mlist, msg, msgdata) File "/usr/local/lib/python3.6/site-packages/mailman/mta/bulk.py", line 100, in deliver self.decorate(mlist, msg, msgdata) File "/usr/local/lib/python3.6/site-packages/mailman/mta/decorating.py", line 32, in decorate decorator.process(mlist, msg, msgdata) File "/usr/local/lib/python3.6/site-packages/mailman/handlers/decorate.py", line 264, in process process(mlist, msg, msgdata) File "/usr/local/lib/python3.6/site-packages/mailman/handlers/decorate.py", line 73, in process for archiver in IListArchiverSet(mlist).archivers: File "/usr/local/lib/python3.6/site-packages/zope.component-4.4.1-py3.6.egg/zope/component/hookable.py", line 33, in __call__ return self.__implementation(*args, **kw) File "/usr/local/lib/python3.6/site-packages/zope.component-4.4.1-py3.6.egg/zope/component/_api.py", line 156, in adapter_hook return sitemanager.queryAdapter(object, interface, name, default) File "/usr/local/lib/python3.6/site-packages/zope.interface-4.4.3-py3.6-linux-x86_64.egg/zope/interface/registry.py", line 348, in queryAdapter return self.adapters.queryAdapter(object, interface, name, default) File "/usr/local/lib/python3.6/site-packages/mailman/database/transaction.py", line 85, in wrapper return function(args[0], config.db.store, *args[1:], **kws) File "/usr/local/lib/python3.6/site-packages/mailman/model/mailinglist.py", line 612, in __init__ ListArchiver.name == archiver_name).one_or_none() File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3278, in one_or_none "Multiple rows were found for one_or_none()" ``` Any following messages to this same mailinglist also get shunted. Somehow the mailinglist ends up with two `mhonarc` archivers, and this causes every message to get shunted. I'm not sure why it always is a `mhonarc` archiver. I'm also not sure how to go about debugging this problem. I have written a script which detects and fixes it, but it doesn't stop the problem from reappearing. The script is as follows: ``` from mailman.interfaces.listmanager import IListManager from zope.component import getUtility from mailman.config import config from mailman.model.mailinglist import ListArchiver def get_list_manager(): return getUtility(IListManager) def get_mhonarc_archivers(mlist, thedb): return list(thedb.query(ListArchiver).filter(ListArchiver.mailing_list == mlist, ListArchiver.name == 'mhonarc')) def remove_last(archivers, mlist, thedb): lastid = archivers[1].id thedb.query(ListArchiver).filter(ListArchiver.mailing_list == mlist, ListArchiver.name == 'mhonarc', ListArchiver.id == lastid).delete() def do_the_thing(mlists, thedb): do_commit = False for mlist in mlists: mhonarcs = get_mhonarc_archivers(mlist, thedb) if len(mhonarcs) > 1: print("{} has {}".format(mlist.fqdn_listname, len(mhonarcs))) remove_last(mhonarcs, mlist, thedb) do_commit = True return do_commit listmgr = get_list_manager() mlists = list(listmgr.mailing_lists) store = config.db.store print() do_commit = do_the_thing(mlists, store) if do_commit: store.commit() ``` Let me know if there is anything else I can provide!