Emacs 25.1, Gnus reads and then forgets nnimap-split-fancy

[Gijs Hillenius]

Using Debian Emacs 25.1, when starting Gnus, nnmimap-split-fancy is read
from .gnus along with other settings, but then, somehow, immediately
forgotten.

When Gnus is done finding new mail and news, I do r g (read Gnus and
check for new messages). Only then the split rules defined in
nnmimap-split-fancy are applied to the INBOX. Instead of say, 12 new
messages, there will be 2, the rest is split across the intended
folders.

When I just began using Emacs 25.1, I found Emacs bug 20610, which
describes the same. Except there
(https://debbugs.gnu.org/db/20/20610.html) the fix that is reported, is
what I already use (or at least I think so).

The suggested fix:
,----
| Putting *both* `nnimap-inbox' and `nnimap-split-methods' in the
| definition of the IMAP select method is *necessary* for fancy splitting
| to work under Emacs 25.
`----

my server configuration in the server buffer:

,----
| (nnimap "thuis"
|       (nnimap-address "server")
|       (nnimap-inbox "INBOX")
|       (nnimap-split-methods nnimap-split-fancy)
|       (nnimap-unsplittable-articles
|        '(%Deleted %Seen))
|       (nnir-search-engine imap)
|       (nnimap-stream tls))
`----

The only difference:

I use:

(nnimap-split-methods nnimap-split-fancy)

whereas the fix prescribes:

(nnimap-split-methods nnmail-split-fancy)))


My "version" works in Emacs 24. I tried the alternative, but that
recreated my entire mail folder hierarchy as news folders, instead of as
mail folders. That was scary.


Any body here have an idea how to debug this?