You may consider the thread you are using - some machines are partial to what kind you use.
My "basic" Singer machine hates 100% cotton thread. I used a full bobbin and 1/2 of another wound with cotton thread - then my machine locked up several times - I rewound bobbins - rethreaded machine - changed needle - then I switched back to polyester thread and it works just fine. I don't know why I could sew with the cotton thread for that long before the machine threw a hissy fit. I was just happy to figure out it was thread causing the problem.