Sewing Machine Videos
Clean the bobbin area. (See video below.) To clean, pull the gray plastic part of the throat plate toward you to take it off. Take the black plastic hook (bobbin case) out of the machine. Clean under there in the metal basket. If you haven't done this before, there's probably lint there.
Inspect the black plastic bobbin case. Do you see any nicks where the needle has struck it? Sometimes you may even see holes where the needle went through, or chunks missing. Sometimes it's more subtle. If you see something, try to buff it out with a fine nail buffer or similar. If it's still rough or chewed up, a new bobbin case is the answer.
ALWAYS use the needle up/down button to get the needle in the highest position before you put the black hook back in. Place the black hook back in there with the green screw facing you and the notch on the right matching the metal bump (you'll know what I mean when you see it.) Now replace the gray plastic part of the throat plate (slide front to back.)
If you ever take the metal part of the throat plate off (the part with the screws), be sure to replace it first, before you put the black bobbin case back in!!
Make sure the thread is coming off the left side of the bobbin as you put it in. When you get the thread in the little slit, pull on it to the left so that the bobbin turns. That makes sure the thread get "seated" in the tension slit.
Make sure you use the needle up/down to get the needle in the highest position before you start threading the machine. Make sure you raise the presser foot before you start threading the machine. Thread it, making sure you get it in the takeup lever (the piece that goes up and down inside the machine while you're sewing.)
Make sure you've got a new size 80/12 or 90/14 needle in it. Try it with a good quality thread on two layers of cotton fabric.
Check out this video I made on Basic Cleaning and Troubleshooting Your Baby Lock Sewing Machine