If your machine doesn't have encoders, then it shouldn't involve the limit switch function in Mach3. Taig does make a machine (the DSLS 3000) with encoders on the motors that uses this function to stop the mill when it gets lost, but that's not the case here. Since the Taig doesn't actually have any limit switches (unless you added some), the only thing I can think of that might be causing this is the Softlimits function in Mach3. That allows you to set up virtual limit switches at certain places, so you can avoid over-running an axis or hitting a clamp. Make sure that function is disabled, and your problem might go away.
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