My bernina record 730 isn't sewing in reverse

I have a bernina 730 record I rescued, it had been sitting inactive long enough to get cobwebs, all that aside I love this machine.

I have taken off the side panel, the motor cover and base to clean and see what was moving and what wasn't. A good clean /oil and I was able to unseize the feed dog knob and get zig zag and the other stitches going again but have no idea where to start /look for the reverse function fix?

Any ideas would be greatly appreciated, thanks in advance.