You need to change the speed in production manager as well as setting it on the cutter.
While that will work, what you really need to do is set the plotter, whatever brand it might be, to not pay any attention to settings sent via software.
Virtually every plotter has this capability. On a Graphtec it's called 'Condition Priority'. It's called other things on other plotters.
Let the software tell it what to cut, let the plotter decide how to cut it. That way you have things varying only in one location at a time. More than that you do not need.