james5 on this form provided me a viewer, https://ncviewer.com/
After I create a drawing I run the gcode file in it, it will show any open segments, I believe is whats happening is what happened to me, I ran mine through sheetcam, if opened it will try to close the loop by creating that arch
Here is my old post, The motion command has an invalid target. G2,G3, and G38.2 - #6 by James5
hope it helps