Whenever I download a YouTube video in .mp4 format, it normally assigns a filename automatically using the title of the video. This feature works just fine for videos in 720p quality. However, when I try to download the 360p version, it does not automatically assign the filename anymore. Instead, it just assigns a default filename of "videoplayback.mp4".
Something must have changed on your end because I only started to notice this issue about two months ago, in late October 2016. Prior to that, this feature was working just fine for .mp4 videos of any quality. I only realized now that I could actually report this issue to you. Anyway, now that I have, I hope you can do something about it.
Apart from that, I think your site is great and that you provide a really good service. More power to you!
Customer support service by UserEcho