In looking into the ‘What is correct chain pitch’, I found that my chains are slightly different lengths.
After hanging the chains from the rafters, I find that my right chain is almost 2 mm longer than my left chain, judging by the 2.3mm pin in the end link:
Looking at the place in the chains that sits on the top tooth for ‘Manual Chain Calibration’ at 1650mm from the sled end, it looks like the right chain is nearly 1mm longer - again based on a 2.3mm pin diameter:
Note that the chain that is longer is not the one stretched for measuring between motors.
Interesting, but I’m not sure there’s anything to do beyond getting some more chain. This doesn’t seem like something software could be expected to handle.