We're suffering from a bug described in hyperkitty:

https://gitlab.com/mailman/hyperkitty/-/issues/408

... but i suspect it's also present in other xapian-haystack
consumers.

This affects at least debian stable, but possibly also
testing. There's an upstream patch that's been pending for a while, I
rerolled it in:

https://github.com/notanumber/xapian-haystack/pull/238

I intend to uplad this to unstable and test a backport soon, ideally,
we'd fix this in bookworm too.