Video Downloadhelper! Is simply the best!
I use it almost every day for more than 10 years. Sometimes download 20 or 30 videos, very fast and easy to use. Never had a problem. I am on payed subscription and when I had a question - VDH(author) answered within hours.
If you see lots of "5" and many "1" - it means "1" are competitors. I read complains - I never had any of problem they write about.
Video Downloadhelper is very stable and powerful!