Toolpaths wondering

I just recently cut a project and it turned out great, i tried to repeat the project and 3x in a row the toolpath wandered, EG… 3mm Endmill for a circle, then a 90Vbit for embossing the edges, the Vbit moved outside the boundaries of the circle, almost like it was moved to the right a quarter of an inch. What would cause this…

BTW i did check my cuts and ensured that they were where they were supposed to me…
Using Vcarve Desktop…

Wayne