You can try increasing the pressure on the pressure foot and going with a larger needle. This sometimes helps. Or at least lessens the number of skipped stitches. HOWEVER, I must tell you that most of my 301's that did this were a hair out of time. The straight stitch was fine, but the minute you start FMQing it would skip because the timing wasn't dead on. And the movements you make with the quilt sandwich while FMQing really test the machine's timing. I've had to retime most of my 301's for this very reason. And after retiming them, the skipped stitching was gone.