machines can be very picky about what thread / needle combos they like and do not like. We have 4 different machines in our house ( I am not the only one that uses them LOL ) and each and every one of them have different preferences for needles and thread. Try a bunch of different thread / needle combos to see what works for yours ! It does not have to be expensive to find out, you only need a small spool of each brand to test with on some small scrap sandwiches until you find what works best, it saves on buying a large cone of thread only to find out your machine hates it. Also, I know this goes against most of what has been heard, my Brother PQ-1500s has NO problems with different threads from top to bobbin. On alot of projects I use surger thread in the bobbin and Essential Threads from Connecting Threads on top. Just play around with your machine and try the unheard of !