Rebuilding terribly engineered laser cutter

[Doddy]

This image says a lot...



It's unclear from some of the other pictures, but this one is particularly interesting as it would appear to show the distortion on spokes projecting radially from the spiral centre, and at a position where the Y axis velocity is tending to zero or accelerating from zero. Is this true of other images? (they are less clear).

Could this be related to torsional elasticity of the couplings/Ali extension bars on the Y-axis?, is it worth trying to drive the two belts separately with two steppers, and removing the length of Ali bar?

Just a random thought