Honda HRD536 uneven roller height

I've just put a new clutch cable on my Honda 536 and noticed that the roller won't maintain an even height from left to right.
When you set the roller height on the left side it is held firm by the height adjust handle, however the right side of the roller can move up or down around it's pivot. I've not noticed this before, but this seems a bad design fault because if the roller is knocked it easily moves to an uneven height.
Don't suppose anybody has one of these mowers and has noticed this.