EDIT: Agree w/ @Hard12find if you’re using a Probe — shift it to the surface of the stock as noted at: https://docs.carbide3d.com/assembly/touch-probe/userguide/#probing-z
The problem here is you seem to be slotting — that’s hard to do — consider the following aspects:
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feeds and speeds: https://docs.carbide3d.com/support/#tooling-support and see https://www.youtube.com/watch?v=S9bceJxpqG0 for concepts on this and https://www.precisebits.com/tutorials/calibrating_feeds_n_speeds.htm for a testing technique and see the series #MaterialMonday: #MaterialMonday on YouTube
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mechanical: https://wiki.shapeoko.com/index.php/FAQ#Mechanical
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geometry — add extra and cut as a pocket with a smaller endmill: Adding geometry to cut as a pocket with a finishing pass
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roughing clearance / finishing passes — I did these by hand in https://cutrocket.com/p/5c9fb998c0b69/