GNUMail: local mail box listed twice

[Svetlana Tkachenko]

GNUMail 1.2.3 on Debian buster shows strange list of boxes on startup:
 - Local
 -- Svetlana
 - Local
 -- Svetlana

Then it connects to IMAP and finds out that it should be
 - Local
 -- Inbox
 -- .. (etc other folders)
 - Svetlana
 -- Inbox
 -- .. (etc other folders)

Then I disable the online Svetlana account
The tree shows this
 - Local
 -- Inbox
 -- .. (etc other folders)
 - Local (no subfolders present here)
It shouldn't show the '-Local' item twice this time. I tried to rename
the second one but it said no.

P.S. I'm not really seeing /what/ gnumail uses for its local mail box,
and I don't know where to find this info - would like to set up
fetchmail to get my messages there...