I have a Janome, too, and love it!
I found out the hard way that thread does make a difference.
I took a FMQ class and decided my Coats and Clark thread would
be just fine----not so. By the end of the class, my thread broke continually and I had nothing but problems. My DH examined the
bobbin area and found LOTS of short pieces of thread. Apparently, the
expensive stuff is made of long pieces of cotton not short ones like the
cheap stuff. So, reluctantly, I made the switch.......