The main reason is that the needle head is not adjusted properly, before install the new needle, be sure to check firstly whether the needle is normal,all needle should stay in a straight line,without deviation;the second is to check that after the needle installed on the machine, needle face the iron plate,whether all needles stay flat on the iron plate,instead of some of the needle already bear against the plate,and other needle is far away,in this case it cannot drill properly;if the front two points is ok,then check if the upper mold hole is enlarged,it may drill deviated when hole enlarged;the fourth point is that the up and down aluminum seat will shake,if the aluminum seat is loose or with serious abrasion,the drilling may also got deviated.