I looked at your Gcode. Are you working in MM or INCH? Your code says it's working in MM but you need to double check three places, your file,your post, and your code. Here are some pics.
I think the problem is line N20 in your code. The picture of the code I posted from my own file you'll see that line but it should have a G53 before it sending the machine to it's home position. I'm also working in inch mode. I'm not sure if that makes a difference in why your post on line N20 rapids the cutter to Z0 . Looking at your code I think you have your clearance set at 15mm and your stock top at 5mm so line N20 would crash unless the post is for some reason dropping the G53. Try this, delete line N20 and rerun.