I recently had a similar issue with my LA. Did all the recommended fixes and still missed stitches in the same area. DH saved the day. He suggests pulling the ribbon cables, and inspect them, if they are full of lint, clean them. Re -insert cable connector at the machine and at the encoder and make sure it is fully seated. Due to oxidation, you may need to use an appropriate electrical contact cleaner on the pins and the ribbon cable connector. Just slight oxidation can cause intermittent connection problems. The connectors used on many of these machines were intended for stationary computer use and not for the constant movement and vibration of a sewing machine (and yes, my husband said to include that).