Check out the spring tension and change or tighten the screw on the bobbin case tencion of or better within the bobbin case placed a circle of fabric or star disc

Your bobbin winder may not be winding properly. u can adjust this by loosining the screw that control the tension and movind the part in the direction where the bobbin has less thread. try tightening the thread tension on bobbin winder. you bobbin case may be defective. clean with tooth brush and use small screwdriver to life bobbin tension device to clean under it. another trick is to cut a piece of nylon the size of the inside of the bobbin case and snip a hole in the middle of the material so it fits in the bobbin case. this wil stop the bobbin from running away, you can buy a bobbin case with built in spring to keep the bobbin from over running. ck your thread take up spring too. very easy to adjust just put screw driver in tension post and turn to right to tighten spring.

Hello Lacinda have a good day to you concern loose or missed stitches please check next: 1-try to change bobbin case with new one. 2-check timing between needle and hook by -make needle bar at lowest position and you can see two mark line at needle bar. -bring the needle bar at second line from down side then check the flat part from needle comes with tip of hook ( if yes means timing is OK , if not means you need to adjust the hook timing . 3-check the ginger guide for hook try to move it foreword or backward to pass thread smoothly. if this is helpful OK if not please send email, i try to do the best to help. best regards ASHRAF ABOZID CAIRO - EGYPT [email protected]