Hello Dan,
I am totally lost on the "A" description. I just do not understand what is being explained.
"If all the other diagonal cuts are nice looking.....you would see the “bumpy” lines on the other sections as well.
I agree. UNLESS....
1. your G-code does not command a straight line, which happens sometimes with segmented code, and the machine is actually moving just as it is told to move.
2. your machine is binding at that particular spot on the axis, which explains your next question-
I don't know what..."Have you physically inspected the axis for the section of that move?"...means.
Binding can be caused by many things. A worn part(s), a misaligned part(s), a badly designed machine, or many other things.
"Racking" or "twisting" of an axis can cause the axis to "jump" or "stutter" when the binding forces are overcome and the axis tries to "catch up", causing what you describe. This usually happens at the point farthest away from whatever is driving the axis (ball-screw, pulley, etc..). In my opinion, this would indicate a poorly designed machine, or the user is pushing the machine beyond its intended limits.
Because the wiggly cuts are only on part of the table, I doubt the error is in the code, but post it here anyways, just to rule it out.
Do you have a link to the machine you purchased?
First, I would go through the machine and make sure everything is aligned and fitted as is it should be, and inspect components for damage or wear.