#suggestionschannel on Discord. If you are on a paid support package you may open a ticket in the client area. Either method will work, ticket made in the client area ensures priority for requests.
This can mean a number of things.
WebMas the file format and
libvpxfor the video encoder with audio off. Turning off timestamps sometimes also helps.
Your version of Node.js is too old. You must have 7.2.0(+). Upgrade to the latest with the following commands.
sudo npm cache clean -f sudo npm install -g n sudo n stable