This is likely to be simply setting up the machine wrong. Take the whole lot apart, off the table, then fix it back on again. Just a simple not fixing the whatevertheyarecalled thingies under the machine that sit on the table & have the claw things to keep them in place and getting those slightly wrong is enough to cause the problem - make sure the main bed is pushed back to it's limit on the table. Then, when fixing the ribber on to it, make sure that the screws are easy to screw in - anything that is difficult to screw in is screwed in wrong. Then, make sure that when she changes the carriage over that the ribber bit is screwed in firmly on the carriage - while it may work for your machine it may not for hers.
Scanthecat.com, April 2009