Sorry to hear that you have had this problem Patricia
I was ready to order my DX7 right around the time I read your post. I did search the internet and all of the reviews (very few) that I could find and did not find anyone else having this problem, so I went ahead and ordered my machine. I have had it for about a week now. The first thing I did when the machine arrived was test the straight stich slide plate. Mine is working perfectly and I have used it often in the past week. I am loving my new DX7 and hope you get your problem resloved so you can use yours soon!