I am going to assume this machine uses a drop in bobbin. After cleaning the bobbin area well, remove the bobbin case itself. There may be a small piece of needle trapped and maybe lots of lint there. You can find a tutorial on how to remove the bobbin case on the internet. Anyone who has a machine should know how to remove the bobbin case as this is an area that collects lots of lint, especially a drop in, and can change the machines performance.It’s not difficult. Trying another needle may also solve the problem.