I have a G carriage and am trying to rib with it on the left side it just keeps going back and forth I had this problem once before but can't remember what i did to correct it. Thanks Suzan
Are all the needles in the main bed, if there are any needles missing it will not work correctly ie go back and forth over a small number of needles.
Are you using your G-points? Those little tan colored things that attach to the needle bed. They make the carriage turn around without having to travel the whole bed? Is the G-light on? Is the G-needle installed? Did you know you can "cast-on" without the needle installed?
Is it set to knit both directions
If you open the trap door where you put the needle in, check the metal pin that holds the trap door hinge. Mine was stuck out a little bit and it caused no-end of problems. It might not be the problem, but its worth checking. Also check the stainless steel strip that pushes in under the garter carriage, it might not be pushed fully in. I had problems with this also after I had the garter stitch jammed. I pushed it back in, but, because it had made the slots loose it kept coming back out with the vibration of the garter carriage, so a machine engineer told me to push it back in place and put a few drops of super glue on the slots just to stop the metal strip vibrating out. it did the trick, not had any trouble since, it might not be this either, but worth checking. Good luck.