Brother Garter Carriage

Hi Anne
I have a little problem with my otherwise excellent garter carriage KG-95. I use it on my Brother KH-894. I can put it on the needle bed from the right-hand side, no problem, but when it comes to putting it on the left-hand side it goes clunk and won’t go onto the needle bed. As you can guess this is very frustrating. I use rails each side of the bed and am beginning to suspect that the left-hand side rails might be slightly twisted.

Also a little bit of one of the two ‘doo-dahs’ (don’t know what to call them, but they are like two little white u-shapes at the back) has broken off. However this doesn’t seem to affect the knitting.
Hope someone can help me with any advice. Also where can one purchase another G-carriage as a spare, just in case old faithful finally gives up?
Best wishes, Mary Langridge