I've had all kinds of problems when my bobbin isn't wound properly. I believe your machine uses a 15 bobbin, so you ought to be able to wind a good one on one of your other machines. Also, you probably know this, but always hold the thread tails for a few stitches when you start sewing - you'll get less bird's nests. I don't know about the needle striking the plate - I have the same problem on an old Morse which is sitting in the garage until I get around to it! Maybe gummy stuff as Miriam said. Best of luck!