grblHAL Alarm 3

grblHALAlarmPosition is lost: home again

The controller was reset while the machine was moving.

Position is lost: home again. The firmware's own message says so. (firmware says)
What to do
  1. Think back: did someone press stop or reset, did the USB cable drop out, or did the power dip?
  2. Home the machine, then set your work zero again before restarting the job.
  3. If it happens on its own, check the USB cable and power supply, and keep the USB cable away from spindle and motor cables.
What users reported CLAIMED · forum and issue reports, not official
  • Repeated Alarm 3 and Error 9 mid-cut on a 3018 Pro. First blamed on electrical noise; the real cause was the cable chain nudging the Z limit switch. (one owner's report) r/hobbycnc thread, Jul 2026
  • Cancelling a job with a soft reset (Ctrl-X) loses homing, so the machine has to be homed again. Users asked FluidNC for a cancel that keeps position. FluidNC GitHub issue #1800
Official grblHAL message: “Reset/E-stop while in motion. Machine position is likely lost due to sudden halt. Re-homing is highly recommended.” source

Got a different message?

Paste it into the decoder. Hamrun's editor checks your G-code before you run it, so a toolpath that leaves the machine's travel or a missing feed rate is caught before the machine stops.

Related codes

Official text copied from the grblHAL source on 2026-11-01. Steps and the position answer are Hamrun's reading unless marked “firmware says”. User reports are labelled CLAIMED.