Spindle stalling every time

I’ve only had stalling on really deep cuts with it contacting both sides. And that was when I was using a 1/4" downcut bit and there was also simply too many wood shavings built up and it bogged down. I’ve had more problem with chattering and losing steps when I was trying to run 600mm/m and 2mm step down in some particularly tough oak. It still didn’t stall - it just loosened up the x-axis so I had play in it. There should be almost no play in the tool head:

There’s definitely something wrong with your spindle if it’s stalling on 1/4" or smaller bits and your step down is 2mm or less. (1mm is usually the most I try) and speed is.

-S