I dont' have a brother one, but if you look at the machine the wheel should be on your right. on the wheel there is sometimes some switches - one normally is set to allow you to load your bobbins. see if there's another setting on there to go forwards.
hmm thats very odd, is the backstitch bit stuck or something, theres usually a little knob on the front that you hold down when you want to go backwards, it might have got mucky and jammed itself? thats all i can think of, thats so strange!
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