Solution: Use desktop software (JDownloader) instead of online converters for files over 100MB.
Solution: YouTube sometimes serves 144p video without audio. Force the downloader to merge the lowest video track with the lowest audio track (OPUS 48kbps). Youtube Video In 3gp 144p Quality Download
Downloading a YouTube video in 3GP 144p is a trade-off. Here is an honest preview: Youtube Video In 3gp 144p Quality Download