There is a small geometry error in the carriage design, I set the spacing for the bolts used to secure the fishing line from the outside edge of the bolts instead of the center. This actually results in measurable error, about 0.4mm as the carriage moves from extent to extent across the bar in the H. So I need to print a new carriage.
The XY Stage is attached to the Arm based electronics, and I need to make a couple of changes to the firmware before I can do any real speed testing, since it doesn't really support acceleration. For point of reference in the video the motion is at about 140mm/s with instantaneous change in velocity (i.e. that's the jerk and velocity setting). I also need to add support for the modified kinematics.
In the mean time if I get a chance I'll set up a test to see if there is any measurable error accumulation over a few hours.