# Spindle ON flag stuck in GUI

**URL:** <https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899>\
**Category:** 🐛 Bug\
**Created:** [November 10, 2025, 12:55pm UTC](https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899 "2025-11-10T12:55:03Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Rollo](https://forum.sienci.com/user_avatar/forum.sienci.com/rollo/32/11035_2.png) [@Rollo](https://forum.sienci.com/u/Rollo)\
**Post date:** [November 10, 2025, 12:55pm UTC](https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899/1 "2025-11-10T12:55:03Z")

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With command M3 and M5 the spindle can be turned ON and OFF but in GUI the Spindle ON flag stuck after first M3  
Only get off in GUI after USB disconnect/re-connect sequence. Same for laser…

> Initial response:  
> [GC:G0 G54 G17 G21 G90 G94 **M5** M M9 T0 F0 S0] GUI: Spindle OFF flag  
> M3 S12000  
> [GC:G0 G54 G17 G21 G90 G94 **M3** M M9 T0 F0 S12000] GUI: Spindle ON flag  
> M5 S0  
> [GC:G0 G54 G17 G21 G90 G94 **M5** M M9 T0 F0 S0] GUI: still Spindle ON flag

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**Author:** ![KGN](https://forum.sienci.com/letter_avatar_proxy/v4/letter/k/c77e96/32.png) [@KGN](https://forum.sienci.com/u/KGN)\
**Post date:** [November 10, 2025, 3:16pm UTC](https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899/2 "2025-11-10T15:16:50Z")

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Yeah that’s a malformed message from the firmware, what are you running?

That blank M shouldn’t be there next to M5/M3 - so our parser is likely parsing the 5/3 for state, but sees a M again right after and replacing the value with nothing because it’s M(nothing).

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**Author:** ![Rollo](https://forum.sienci.com/user_avatar/forum.sienci.com/rollo/32/11035_2.png) [@Rollo](https://forum.sienci.com/u/Rollo)\
**Post date:** [November 11, 2025, 12:44am UTC](https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899/3 "2025-11-11T00:44:55Z")

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oh yes you are right. It looks like a firmware ‘glitch’. Didn’t see it on CNCjs as the G-Code parser seems to be more robust. I will try to find a way to suppress it but may be you can target the same robustness in gSender 🙂

_tested on:  
LUNYEE 3018 PRO ULTRA  
Firmware: Monport [VER:1.1f.20230316:] [OPT:VMZHL,35,254]  
gSender 1.5.6 on RPI4 connected via USB to LUNYEE (Grbl)_

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**Author:** ![KGN](https://forum.sienci.com/letter_avatar_proxy/v4/letter/k/c77e96/32.png) [@KGN](https://forum.sienci.com/u/KGN)\
**Post date:** [November 11, 2025, 6:21pm UTC](https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899/4 "2025-11-11T18:21:00Z")

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We’ve added some logic to ignore storing command letters without a corresponding value which should resolve this in the next release. No guarantees though because we don’t have a version of the firmware with incorrect reporting.

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**Author:** ![chrismakesstuff](https://forum.sienci.com/user_avatar/forum.sienci.com/chrismakesstuff/32/10759_2.png) [@chrismakesstuff](https://forum.sienci.com/u/chrismakesstuff)\
**Post date:** [January 5, 2026, 6:56pm UTC](https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899/5 "2026-01-05T18:56:17Z")

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@Rollo how’s this looking for you now?

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**Author:** ![chrismakesstuff](https://forum.sienci.com/user_avatar/forum.sienci.com/chrismakesstuff/32/10759_2.png) [@chrismakesstuff](https://forum.sienci.com/u/chrismakesstuff)\
**Post date:** [January 16, 2026, 5:07pm UTC](https://forum.sienci.com/t/spindle-on-flag-stuck-in-gui/24899/6 "2026-01-16T17:07:09Z")

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Closed on January 16, 2026, 5:07pm UTC