Brother Ribber Carriage KH850?

I dropped my ribber carriage KH850 from my lap onto the carpet and it is now not working properly. instead of gliding across the needles it is very stiff and it is dropping off all stitches going right to left from left needle 15 to the end of the bed. I have cleaned, and oiled it and everything looks as if it is working - all buttons seem to be operating, but it is not working properly. Any answers would be very much appreciated.