Bogofilter with Claws Mail, seems not to act on spam

[Adrian]

Thanks to people on this list I have migrated my wordlist and am using
it on a new version of Claws Mail with a new version of bogofilter.
It goes back many years* and I have a 30MB .db file.

*oddly the oldest date is March 2023 though it looks like some entries
are older.

But the problem is, though I faithfully mark all spams, I'm not seeing
the effects.  Claws is set to move them to Trash and nothing ever is.
I do seem to see many fewer spams using my home Claws than using other
clients that don't filter, which suggests that it's silently deleting
them, but that's not the behaviour I set.

I know this is likely to be a question for Claws, but I'm loth to put my
head into the lion's mouth that is the Claws users list without having
all my facts ready.

My initial question is, how can I test an individual message saved as a
file with all headers?  The command-line examples in the FAQ are mainly
for maildirs mboxes and MH and the only ones that seem to use individual
files are in the instructions for specific mail clients such as this one
bogofilter -n -v -B "%f".

I've tried "bogofilter -B -n -vv mail.txt " and "bogofilter -B -n -vv
<mail.txt", but all I get out of this and similar commands is
# 0 words, 0 messages

What command should I use to get a report on a single message saved to
file?

Claws doesn't write an X-Bogosity header back to incoming mails for
some mailbox formats, this is something to do with them being in memory
at the time.

Many thanks, Adrian