[MM3-users] Unusual behavior: Standard discussion lists with prefix are sometimes having prefix *dropped*

I noticed some unusual behavior in Mailman3 stable release on PyPI and such.  Namely, there are instances where replies are being processed and the prefix tags are simply being **lost** and dropped by Mailman3, instead of being properly prepended where they're supposed to go.

Is this a known bug or does it need its own bug in the gitlab tracker?

Thomas