If your using the standard DW660 mounting bracket I found that if the DW660 is rotated a certain way it hits the bolts. It drove me nuts for a week until I figured it out. Rotate the 660 a little. I attached a couple pictures
I am now using the universal mounting system so I can swap out between a hot end for 3D printing and my Dw660. I noticed that the universal mount has a little more clearance.
Just a thought. good luck