Is there any sort of list of steps to take to diagnose a cutting error problem?
Egg shaped circles are probably do to some axis mechanical problem
and think the figure 6 may just be a lead in.
If the machine is accurate, mechanicaly good,and proper application of gcode provided,
the piece should come out correctly.
1. Just do some actual cutting tests on "simple " things like a cicle, rectangle / square
and see how accurate the machine cutting is with tooling, material and settings you will use.
Optionaly you can just trace the gcode pathing onto a surface with the machine running but no
depth of cut for a quick visual inspection.
2. For gcode testing, see how the gcode loads and that there are no errors, step thru the coding,
or simulate if sometyhing is more complex.
I backplot the gcode and review in CAD to check pathing, but one needs backplot software to do it.
RICH