this error occured in Chrome with Nginx serving a static file: ".../static/js/vendor.c4ed7962fb4a63ad3c3b.js net::ERR_CONTENT_LENGTH_MISMATCH 200 (OK)"
root disk was full; after cleaning tmp files the error disappeared.
to prevent: make sure your disk remains clean ( a script such as this could help:https://crunchify.com/how-to-automatically-delete-tmp-folders-in-linux-automatic-disk-log-cleanup-bash-script/ )