This occurs in both iOS and Android devices based on testing from multiple users. It only seems to occur in very long threads, as it was found in The Penalty Box over in the United forum. When posting, an error is returned to the user: "Error - The remote server sent an unknown response. This could be a result of the forum software plugin being outdated or having a conflict." The error occurs when making a reply to the thread, either with or without a quote included. Liking posts does not generate the error.