I've used Gnus for some number of years, pulling email via POP3 while leaving it on the server. I've done this from gmail for at least 5 years, I think.
Not too long ago, I moved from Debian Wheezy to Jessie, and it stopped working. I was busy and didn't work on it for a while, but I just tried again, found that I couldn't log into gmail because I lacked an app password, and apparently fixed it.
I entered `3 g` and waited while gnus grabbed a few months of email. Then it said it was moving them, as it should with nnsplit. Finally, it gave me an error: `gnus-get-unread-articles: Wrong type argument: numberp, y`
I ran (setq debug-on-error t) in the scratch buffer and restarted Gnus. It did the same thing, and then I ended up with this in a backtrace buffer:
Debugger entered--Lisp error: (wrong-type-argument numberp y)
gnus-setup-news(nil nil nil)
byte-code(" \204 \204 \306 \210\202L\307\310!\210\311\n! \f\204
\203!\312 \210\313\314 #\210\307\315!\210 \2036\316\317\320\"\210\321 \210\322 !\210\323 \210\324\325!\210\326 \210\307\327!\210\314\207" [dont-connect did-connect gnus-startup-file gnus-current-startup-file gnus-slave gnus-use-dribble-file gnus-group-quit gnus-run-hooks gnus-startup-hook gnus-make-newsrc-file gnus-dribble-read-file gnus-setup-news nil gnus-setup-news-hook gnus-request-create-group "queue" (nndraft "") gnus-start-draft-setup gnus-group-list-groups gnus-group-first-unread-group gnus-configure-windows group gnus-group-set-mode-line gnus-started-hook level gnus-agent] 4)
gnus-1(nil nil nil)
call-interactively(gnus record nil)
call-interactively(execute-extended-command nil nil)
Does this make any sense to anyone? Anything else I should look at to figure this out?
I'm running Gnus v5.13 on Emacs 24.4.1.