Safe - 1 thread BUG

Every time I am trying to download a playlist, 4K Downloader picks random videos to download, and sometimes it even starts another video without finishing the previous one.
Sometimes I end up with some videos downloaded, while most of them started downloading, but hang up. 4K Downloader starts other videos randomly but refuses to finish the job.
I have to close the app. and redownload all the videos that were hanged up is the progress was happening in the previous session.
After I restart the 4K Downloader, it seems to do a better job in the second session, restarting to download the unfinished files one by one.

Is there a way to force 4K Downloader to finish downloading the videos one by one without starting other jobs. The "Safe - 1 thread" isn't always 1 thread.
This also raises a further problem is a feel 4K Downloader when it hangs up in the middle of the download and goes to the next video, some data corruption is happening. After the video is eventually downloaded, half of the video doesn't work or frames are skipped.

These are the playlists I had problems with, but most of the time 4K Downloader is unreliable. Sadly, sometimes I have to open my Mac and use Downie as it does a much better job.
https://www.youtube.com/playlist?list=PLD8AMy73ZVxUCR0MaqEwcPx7-wwEdfJwL
https://www.youtube.com/playlist?list=PLD8AMy73ZVxXzY8MUXCsk9DpzxLYuMebh

I would love to see this app fixed, without video data corruption and without randomly skipping half-downloaded files.