So, I get issues with mods like "Mushroom Cloud Patched" or "Better Artillery Sounds".

73.173 Error ModManager.cpp:1577: Failed to load mod "betterartillerysounds": betterartillerysounds/data-final-fixes.lua:58: attempt to index field 'action' (a nil value)
stack traceback:
betterartillerysounds/data-final-fixes.lua:58: in main chunk

I added a print to see which component was causing trouble, and it is atomic-artillery-projectile-rampant-arsenal .

Looking at your code, there seems to indeed be places where this item is built with no 'action' field (eg Artillery.lua:632), I suspect this is an oversight, action should be the 3rd argument of makeArtilleryShell not the 2nd one, and you apparently have code to deal with nil action in ProjectileUtils.lua:487, but this code is commented out.

Final action is what happens in the shell reaches its final destination.
Action is what happens on every intersection between its firing point and final destination.

I've added this to the list of todos, but currently this is a low priority because it is functional. It may be worthwhile to bring up to the other mod authors.

this should be fixed in the latest