Thanks for your feedback again. It turned out that upgrading our components to the listed 3.1 suite versions *and* fixing permissions on /var/www/.cache helped significantly. We still get database locked errors, but much more sporadically, and the application is more responsive in general.
However, we haven't been able to switch to postgresql. We did do a django "migrate" for sqlite due to the new version, but when we then backed up the sqlite and tried to load it into the new postgresql database, we get:
hyperkitty.models.email.DoesNotExist: Problem installing fixture '/opt/mailman/mailman-suite/mailman-suite_project/dump_sqlite_updated.json': Email matching query does not exist.
Interestingly, this seems to be the same error as perhaps the most common one in our uwsgi-error.log (see my previous message), which is still seeing constant activity. Any suggestion of how to overcome this?
I have tried to compare our settings to the example ones, and haven't found obvious culprits, but I will take a closer look.