Getting language_not_allowed error, when commenting anywhere from my instance

I only see the error in the logs of the instance's backend. It looks like this:

ERROR HTTP request{http.method=GET http.scheme="http" http.host=my.host http.target=/api/v3/ws otel.kind="server" request_id=9b6fce13-83ef-40be-bcef-9771bf0af7b5 http.status_code=101 otel.status_code="OK"}: lemmy_server::api_routes_websocket: language_not_allowed: language_not_allowed
   0: lemmy_api_crud::comment::create::perform
           with self=CreateComment { content: "content", post_id: PostId(1), parent_id: None, language_id: Some(LanguageId(37)), form_id: Some("comment-form-5zOoMA7fIkVI2XvABLvr"), auth: Sensitive }
             at crates/api_crud/src/comment/create.rs:42

First of all, I don't understand, where the error originates from - lemmy.ml or my instance? Second, what it all could mean, and what I can do about it?

I tried changing the languages around - in the settings of my server, my user, and under the comment itself. I get the same error every time. Right now, everything is set to "English"