Probe Turned on while in the Spindle and I can't replicate this error!?!

TLDR: Probe turned on in the spindle and I can't replicate the error - I am now living in fear of the same thing happening again because I can't replicate it.

OK, First up - Machine
I have a PrintNC style machine, Mesa 7i76e, I'm running LinuxMint and LinuxCNC 2.9 with Probe Basic on top. I have github.com/TooTall18T/tool_length_probe this subroutine for toolsetting. I have both a toolsetter and a 3d probe.

Second, what happened

1. I started and homed machine like normal
2. I typed "99" into the tool window in the lower half of Probe Basic and clicked M6 G43 button
3. The machine moved over the toolsetter and I loaded T99 - the probe
4. I clicked "OK" on the window saying the tool has been loaded, and he probed the length
5. I used the probing subroutines on the probe basic window to find my 0,0,0 location
6. I want to have a 1mm extra offset upwards on the Z axis, so where it now specifies 5 in the lower half of probe basic for the G54 work location (since it backs probe off in Z) I typed "4" and pressed enter. This moves my G54 Z0 up 1mm further.
7. I pressed the "go to zero" button, so that he went to the G54 0,0,0 - to verify that this location was correct
8. I loaded my file from Fusion360, and pressed start
9. What I expected to happen was that the machine would raise up to G53 Z0, move over to toolsetter, and ask to load T8
10. What actually happened was that the machine skipped the first few instructions and turned spindle on
11. I hit e-stops and cried because my cable was broken

The beginning of my Gcode file - it appears he skipped N20 G53 G0 Z0 and N25 T8 M6, and probably some other instructions too

%
(10 Inside P2)
(T8  D=8. CR=4. - ZMIN=-27.25 - BALL END MILL)
N10 G90 G94 G17 G91.1
N15 G21
(WHEN USING FUSION 360 FOR PERSONAL USE, THE FEEDRATE OF)
(RAPID MOVES IS REDUCED TO MATCH THE FEEDRATE OF CUTTING)
(MOVES, WHICH CAN INCREASE MACHINING TIME. UNRESTRICTED RAPID)
(MOVES ARE AVAILABLE WITH A FUSION 360 SUBSCRIPTION.)
N20 G53 G0 Z0.
(RAMP3 3)
N25 T8 M6
N30 S17500 M3
N35 G54
N40 G64 P0.01 Q0.01
N45 G0 X-1.693 Y-17.186
N50 G43 Z16. H9
N55 G00 Z-25.656 (Changed from: "G1 Z-25.656 F4000.")
N60 G01 Z-27.25 F4000.0 (Changed from: "Z-27.25")
N65 G3 X-1.194 Y-18.577 I0.538 J-0.592
N70 G1 X-1.045 Y-18.584

I tried to replicate the error by following the steps above, but it functioned normally and operated as expected. I should also mention I've been using this setup for a few weeks without any issues prior to this.

Any ideas as to how this could happen? I am a bit afraid of an error that I can't replicate because I don't know how to avoid it in the future, and imagine myself just waiting for a ticking time-bomb of this happening again in the future.

I'm not sure what other information could be handy in helping to diagnose this.

Memory is fuzzy, but...

If you have the Probe Basic main screen up, and the program loaded, I believe it's possible to accidentally initiate a sort of 'run-from-line' function.

The gcode file will be displayed with the first line highlighted.  OP will need to experiment, but I seem to recall that if you use one of the keyboard arrow keys (up/down) to highlight different lines and then press cycle start it will start from whichever line is highlighted.

My PB install isn't available for testing, but should be easy enough for OP to test.  I could be totally wrong here but I remember from testing a while back that there were some weird behaviors with the PB g-code editor and display.

I've been a bit slow in catching back up here - but I've got two things to try come Friday or Saturday and I'll report back.

1) Seeing if I can get it to run-from-line when hitting "cycle start" - I don't believe it's likely as there is a separate run-from-line button that I didn't press (and I use mouse/keyboard so no fat-fingering on the display), but perhaps it happens - I will try a bunch of permutations of this.

2) Perhaps what is more likely and something I had done after some more reflection and talking on the LinuxCNC discord - I had previously typed in M3 S24000 to manually jog and face something, and only typed M5 to stop the spindle. Perhaps having S24000 somewhere allows it to get activated?

In any case, thanks for your feedback and hopefully I can dig down to the bottom of this soon

Yea, that's a doozy.  Please let me (us) know if/how you nail it down.