I have added -t 72000 (20 hours) to force ffmpeg to mux the file when a "time jump" happens.
For some reason every job I've seen so far (at least 6 in total) was to 20 hours or more.
I think It's a safe value, which won't cause any troubles. There is no chance recording a live stream for 20 hours without interruptions anyway (my record is 3 hours).
https://github.com/rg3/youtube-dl/issues/2213
A suitable downloader can be found using the 'get_suitable_downloader' function.
Each subclass implements 'real_download', for downloading an info dict you call the 'download' method, which first checks if the video has already been downloaded