nnimap problem - old headers in summary buffer

[Andreas Balser]

Hello,

I have the following problem running gnus v5.10.8:

When I move email messages from one folder to another, the header of
the moved message is still shown in the summary folder of the old
folder. (After I leave the folder and enter again; or after I quit
gnus/emacs and start it again.)

Some of those messages can still be read, and some not.

Both kinds cannot be erased by "B Del" (because they aren't there
anymore). 

How I can I make gnus create a good summary for such a mail folder?

Regards,
Andreas