Putting this into my local config /etc/mailman3/mailman3-web.py:
Q_CLUSTER = {
'timeout': 300,
'retry': 360,
'save_limit': 100,
'orm': 'default',
'poll': 5,
}
..fixed the problem. Looks like the default had no 'retry' and
defaulted to something less than 300, possibly 60,
David Koski
