Are you sure your board is not warped a bit from clamping down the edges? The down cut bit also pushes the board down and the tool up causing opposite flex of gravity, think of the whole thing like a spring being pulled down by gravity any help opposite of gravity is exagerated. Most people would got at least a few mm through your stock .1mm is not enough. A regular bit pulls the tool down and the material up, this is how the machine is pre-stressed from gravity, and gets a bit more accurate in the z direction either way .1mm is about 10x’s too little overshoot.
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