Seems to be a compatibility issue, reaching note 12 tries to unlock a new research in a way that conflicts with Factorio and Conquer.

The crash:
Error while running event field-notes::on_nth_tick(300)
The mod ○🌐Factorio and Conquer: Tiberian Dawn (2.0.14) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Factorio-Tiberium::on_research_finished (ID 22)
Factorio-Tiberium/control.lua:1975: bad argument #1 of 3 to 'insert' (table expected, got nil)
stack traceback:
[C]: in function 'insert'
Factorio-Tiberium/control.lua:1975: in function <Factorio-Tiberium/control.lua:1970>
stack traceback:
[C]: in function 'newindex'
__field-notes/control.lua:112: in function 'sync_detected_force'
field-notes/control.lua:817: in function 'mark_player_detected'
field-notes/control.lua:877: in function 'maybe_corrupt_turret'
field-notes/control.lua:1037: in function <field-notes/control.lua:1029>

Steps to reproduce:
Install this mod with Factorio and Conquer.
Create an extremely dense cloud of pollution, the best way to do this is by spamming dirty bombs from Schall Radioactive Waste.
The first 11 notes will trigger without issue, note 12 will crash.

Thanks for the feedback! Exactly what I need to debug this. I think it might have to do with factions, as node 12 does some changes under the hood. I will check this and let you know once I have a fix (if that is possible).

Good news! I managed to fix this and found some interesting behaviours on the way, which should make note 12 even more interesting. I reproduced the error exactly as yours, and, after the fix, the save was fine and things are working as expected, so you don't lose your save.