It’s not uncommon to get skipped stitches when sewing, especially after sewing a few projects . If you experience skipped stitches change your needle. Needles wear out due to the constant friction. Some materials such as Batiks are harder on the needle and require a needle change between projects. Good quality needles are important. Schmetz makes a great sewing needle. There are also titanium coated needs that last through a few projects. If you are a Longarm Quilter you probably use a 40 wt. thread if so, you want to use a #18 needle; although, I frequently use a #16 in my Bernina Q24 and it seems to work just fine. Unless you are using a titanium needle, I recommend change your needle every time you start a new project. If this doesn’t work, clean out your bobbin case area. It’s surprising how much thread dust builds up inside the machines.