Stiching. the upper thread snag in the shuttle below and break. I have tried adjusting the

Question

the upper thread snag in the shuttle below and break. I have tried adjusting the tension without success. I place a new needle without success.The machine stich 4-5 stiches and suddently break the thread. Ussually one full loop or two of upper thread is tangled in the shuttle where the lower thread bobbin is located.