Sorry for a late reply! I have many mods, notifications, while mostly out of Factorio playing myself for last couple of years...
Well, I don't think this mod can be the issue's cause – in Factorio, desync happens due to mistakes in runtime code, and this mod has no runtime scripts, only declarative prototypes which define weapons and items the same way the original game does. You either:
1. Enable this mod without your son turning it on too,
2. Have some other mods which behave wrongly – which might be triggered by changing enabled mods, but not by this one directly.
If the issue is still actual, let me know which other mods do you use!
