The culprit, some Ace had decided to skip the grub screws that lock the black collar and it had undone letting the gear cluster slide left. I consider it lucky the gears didn't crash or chip.... Email sent and as yet no response. Time is ticking as I need to get these parts done, I retightened the collar and checked the gears. Then I went fishing with a magnet to see if the grub screws happened to be at the bottom of the oil bath.... Nope, and looking at the collar in locked position no sign the thread ever had a screw bite onto it.
Break out the 8mm threaded rod and prepare to Grub thy Screw....
Be careful how you grip threaded rod as it is easy to crush the thread. My preference is to use two nuts, the front one slit so it grips like a collet. The rear nut just keeps the rod centred. Cut a small shoulder to clear the threads and another to clamp a copper disc down when we install the grub screw. You might want some paper shim on the front nut to allow for it closing down and take the load of the rear of the jaws. Bits of beer can work well too, both for shim or gripping the threaded rod directly.