Passap E6000?

The jaws which hold the yarn carrier do not move from right to left or left to right as I move the carriage along the bed. They do not open to pick up new yarn. hence I cannot knit. When i take the lock of the bed i can move the jaws easily.
Ive tried another back lock and it seems to grate as it starts at edge of bed and drops stitches intermittently and then about 12 stitches at the beginning of the row. All problems occur on right to left movement.