Great tutorial to learn about issues you may be having with these things. I came across it while looking for information on why my Janome will not sew stitches consistently. DH checked the timing and it is still lined up correctly.
I like the big needle in the video. It shows the big groove above the eye in all needles that makes it easy to thread the needle. I broke my auto-needle threader and was happy to learn, previously, about the groove. If you just push your thread against the shaft it will fall into the hole! I used to get on my glasses and hunch over and try so hard to "hit the hole".