Here's where you get to cry a bit. There's a lot of various debugging steps. First you're more than likely going to need to do this process at the very least:
I find that the stop button doesn't really work well when the G-code is running. It'll keep running for a bit. If it's a true emergency, unplug everything - it's the quickest way.
<aside> Another gotcha is that if you do manage to stop the Maslow mid-cut, it will NOT lift the bit to safety height. You'll need to do that manually, so make sure you lift the bit up before you start moving the Maslow around or you'll at best gouge your work piece, and at worst break the bit.
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The Maslow community is quite helpful. If you're still struggling after trying these fixes, consider posting your issue on the Maslow CNC forums with detailed information about your setup and the problem you're experiencing. Often, someone has encountered the same issue and can provide specific advice.