We're having some localised thunderstorms here today, so lightning strikes mean it is best to shut down equipment, so I have had to get offline, sorry
I am in Australia, so our time difference will mean a delay in responses, as you will be around 17-19hrs behind us
If you remove the thread and bobbin, does it perform as you would expect ?
New Needle is the first thing in these cases.... and a good clean of the bobbin and hook race area... I expect you have already done these
Which Model do you have ?
Check the tip of the Hook for any burrs (a fine emery board is good to polish smooth)
Run your finger around the edge of the Hook Race and check for burrs too
"The needle goes down and sticks".... do you mean it jams and will not go up again ?
The better the detail, the better I can try to assist
Let me know how you get on, and please get back to me if you have any other questions or concerns and I will try help you more. It may take more than one exchange to get a fix, so please work with me, you are my eyes and ears here
If you feel that I have helped to answer your questions or lead you to a solution, please remember to rate my performance positively before you leave so that we can close the file as it is the only acknowledgement we receive for our time and experience.