can't download

I have been using 4K Video Downloader for a year now, and it has been working perfectly until recently. Now, certain videos downloaded through a playlist cannot be download, with the 'can't download' error coming up. After closing down the program and reopening it, these videos then download perfectly. It is the most recent version, and all the videos are taken from Youtube. I have uninstalled and reinstalled the program, but it keeps happening