Experiencing .txt, .json and .docx upload failures. Image files like .png upload fine

Small .txt and .docx and .json uploads fail across both ChatGPT desktop app and web app. A UTF-8 test.txt file containing only “text” hangs around 75% and sometimes shows a red “Unknown error.” .png uploads work normally. I tried multiple file names and contents. This does not appear to be file size, token count, encoding, browser, or desktop-app specific.