The take up lever is normally the culprit. However, using a Microtex 90/14 needle will also help...or a topstitch needle.
Nine times out of ten with skipped stitches it is the needle. Nesting under the plate is normally the upper thread....and that leads to the thread out of the take up lever. Janome has had this issue of thread coming out of the lever and subsequent machines like the 8900 and their embroidery machines have a locking take up lever....once your thread is int he lever, there is a little piece that comes down behind it and locks your thread in.