I bought my grand the Hello Kitty 3/4 machine at age 8 and she is still using it and she's 19 now. I was told at the dealer that the 1/2 size is considered a toy machine and the dealer would not service it at all. As far as the machine coming unthreaded that would be frustrating for anyone. I assume you have sewn on it yourself to try to figure it out.
Does it come unthreaded while sewing or starting sewing or end of sewing?