Why is my 1st pass out of alignment?

Hi folks,

Having an issue where my first pass is about 1mm off in the x axis, but successive passes come out as expected. I’ve seen it in both positive and negative directions on the x axis.

I’m using a .125" square end mill on a Shapeoko 3. I’m cutting 1/4" baltic birch plywood that I’ve secured with double sided tape.

Here’s a screen shot of my settings. I’m using default Carbide Create values.

Any suggestions on how to correct this?

Check your pulley set screws.
Check the belt tension.

Please use the checklist: