When the carriage jams it may be that the machine main bed has not been set up properly or the carriage has been dropped. If this also happens when you put the carriage on either end of the machine then it may be a loose screw on the carriage.
Another reason may be that you have a needle which is bent - that does not mean you can see where it is bent as this may only be noticeable when it is brought forward by the carriage movement.
Scanthecat.com
April 2009
Automatic Answer
While you wait for answers, we may have found some information which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix knitting machines.