tempus The AM5 is the biggest lottery of the astro world at this point.
Nah, the USB hardware in ZWO products beats the AM5 by a mile :-).
The AM5 simply is QC'ing the wrong thing. They are QC'ing the amplitude of the periodic error (and still boasting about it for the AM3), while the parameter to QC is the first derivative of the curve.
They should trash the gears with the large slopes instead of passing it to the customer as a usable product. (Note that large harmonic distortion means large slope by the chain rule of calculus. So, when you see lots of wiggles in the curve, run, don't walk, to return the stuff.)
And if I am not wrong, they have even reduced the period of the AM3 from 430.82 seconds down to 288 seconds. That would instantly bump the already large slopes of the strain wave gears up by another 50% (again, from the chain rule). What are they thinking?
It is not clear, but I saw recent spec for the AM5 to also have a 288 second period. It is either a documentation error, or that mount has been revised too to the shorter period.