On new toolpath operations, spiral for example, the step size will sometimes default to 0.00, which will result in a program crash because, I'm assuming, infinite loop. Could there be a warning box or something that prevents 0.00 step size?

Thanks for the feedback! Yes, in some situations the step size will default to zero inadvertently. I will add a warning/error if the step size is zero for situations where it absolutely shouldn't be (with horizontal milling you can legitimately set it to zero to generate a finishing toolpath), and perhaps do the same for the cut depth parameter too. Really all of the parameters pretty much should have some kind of verification, it's a little tricky because different operations can interpret or apply them in different ways but keeping the step size away from zero is a good start. That'll be in for v1.41a which I'll be putting out this week :) Thanks!

Charlie