Gotta be coming from LazyCam. The original DXF is via InkScape and is designed as if it were 2D --Like you were going to run it through a laser cutter. All depths, pockets (if there were any), passes and tabs are all done in Lazy. I can post the DXF if you like, but there is nothing special there at all. I can draw a square with a circle in the middle and replicate this issue each time. Oh, and yes, the bit information is spot-on --Depth per pass, feed rate etc. all are correct during the normal milling process. This "dive" is at a depth greater than the "max cut" I have set for the bit.