Just watched the video, lots of good points, found out something I've been doing since I learned to sew!
He said, when you put the bobbin back into the machine, not to hold on to the toggle, but to keep it closed and put the bobbin in and jiggle it until it seats. The toggle is the lever on the back of the bobbin case. It was worth watching just to see I've been doing that wrong. Great, simplistic video for tension problems and how to correct them.