Elisp function throws error only when called while init.el is open in buffer - debugging

Question

I am using Emacs, and wrote a custom function in init.el to make it easier for me to create Anki flashcards upon press of a keybind. This specific function is used to retrieve two values (using Anki-Connect) and let me choose them from a list (the function is based on behaviour found in anki-editor.
In order to do that, I declared a few variables outside the function, so that I can later use their values in a org-capture-template. They are set to nil at the start because I check somewhere else if they have already been set and otherwise call the below function first.
My solution works, but only as long as init.el (or Emacs.org, from which it is compiled by tangle) is closed. If I call the function while init.el is open, I get the following error: "Wrong number of arguments: (3 . 3), 2" - I do not understand why that happens.
How can I fix this problem?
My code looks like this:
(defvar my-anki-deck nil)
(defvar my-anki-notetype nil)
(defvar my-anki-fields nil)
(defun my-anki-set-deck-and-notetype ()
(interactive)
(setq my-anki-deck (completing-read "Choose a deck: "
(sort (anki-editor-deck-names)
#'string-lessp)))
(setq my-anki-notetype (completing-read "Choose a note type: "
(sort (anki-editor-note-types)
#'string-lessp)))
(setq my-anki-fields (progn
(anki-editor--anki-connect-invoke-result
"modelFieldNames"
`((modelName . ,my-anki-notetype))))))
Below is the detailed error message (I tried to format it nicely, this is the best I was able to do):
Debugger entered--Lisp error: (wrong-number-of-arguments (3 . 3) 2)
request--curl-callback(# "finished\n")
anki-editor--anki-connect-invoke("deckNames")
anki-editor-deck-names()
(sort (anki-editor-deck-names) #'string-lessp)
(completing-read "Choose a deck: " (sort (anki-editor-deck-names) #'string-lessp))
(setq my-anki-deck (completing-read "Choose a deck: " (sort (anki-editor-deck-names) #'string-lessp)))
my-anki-set-deck-and-notetype()
funcall-interactively(my-anki-set-deck-and-notetype)
command-execute(my-anki-set-deck-and-notetype record)
counsel-M-x-action("my-anki-set-deck-and-notetype")
ivy-call()
ivy-read("M-x " [evil-collection-magit-toggle-text-minor-mode table--measure-max-width vc-src-responsible-p lsp:omnisharp-run-tests-in-class-request-column nexti tramp-completion-handle-file-name-all-completions term-do-line-wrapping lsp-watch-kind? speedbar-check-vc-this-line access-label curr-btn magit-revision-filter-files-on-follow treemacs-dom-node->set-position! calcFunc-rgrade term-handle-exit &error rng-parse-validate-file magit-xref-insert-button speedbar-file-regexp gnus-agent-group-covered-p evil-collection-org-maps edebug-mode-on-hook message-expand-name-databases C-i autoload-find-file c-make-ml-string-opener-re-function gnus-try-warping-via-registry magit-list-modified-modules pullreq_label:pullreq gnus-server-compact-server :odt-styles-file gdb-thread-number :mac org-table-get-range vc-bzr-shelve-menu rng-match-infer-start-tag-namespace Above nnimap-status-message gnus-summary-limit-to-marks treemacs--get-label-of nnmail-message-id-cache-file treemacs-python-executable article-fill-long-lines smime-buffer-as-string-region lsp:set-file-operation-pattern-options? diredfl-symlink Parchment c-default-value-sentence-end rg-elisp-font-lock-keywords posframe-poshandler-frame-bottom-left-corner ...] :predicate #f(compiled-function (sym) #<bytecode -0x11c32b217e0c370d>) :require-match t :history counsel-M-x-history :action counsel-M-x-action :keymap (keymap (67108908 . counsel--info-lookup-symbol) (67108910 . counsel-find-symbol)) :initial-input nil :caller counsel-M-x)
counsel-M-x()
funcall-interactively(counsel-M-x)
command-execute(counsel-M-x)