Thanks for the quick reply. We have over 2000 lists but a relative few receive large amounts of spam or unusual amounts of messages which aren't intended to be delivered to list members. We've been using Mailman for decades so there's been a lot of creative applications for the system which do not correlate to a standard discussion list or listserv.
I'm currently removing 2800 messages from one such list via Python shell and it's been going for 16 hours now. It's only half done.
I had previously increased timeout settings so that Postorius would not cause a browser timeout. That helps the vast majority of our list owners/moderators do what they need for small batches of messages.
I'll try replicating this latest issue in my test environment where logging is easier to inspect.
I'll follow up with my findings and more questions.
Thank you!