QUOTE-I have noticed that the quality of some lower priced threads seems to be getting worse. I don't know if that was your problem but I really like the Aurifil now (even if it is pricey.-QUOTE
Just saying, I've had good experiences with connecting threads thread as well.
I don't know a lot about different machines and at times mine is a mystery, but mine makes grinding noises when it has to do with up and down of the needle shaft lever.