Good suggestions. Also, try a product called Sewer's Aid. It comes in a small bottle that looks like Fray Check - don't get them confused!. It's a liquid silicone that you put directly on the spools of thread and it helps them run through the machine very smoothly. It's really great for metallics, but it helps no matter what kind of thread. It's made for this, so it's not going to hurt your machine, either. My machine is sometimes finicky too, but this, in addition to the things listed above (I use UNwaxed floss, BTW), have solves the majority of those issues.