Hello there.
Without seeing the full error message, I can't be sure what's causing it. $Datas by itself is not something my plugin (or any other) is likely to be calling.
When you get the error, open the console (f12) and click on the console tab at the top, and then take a screenshot of what you see in that window, and paste it in a comment here. Also, I'll need to know what you're doing when the error comes up. Is this happening when you click test play? When you load a save file? When you open the menu? When you try to go into the crafting menu scene? What you call a plugin command? These are all important things I need to know to try to track down the problem.
My initial thought was that maybe you weren't running the CraftingCore plugin, but I realize now that if that were the case it would give a very specific crash message before loading at all.
Also, if you could post a screenshot of your plugin manager (or multiple if you have too many plugins to show in one screenshot), just so I can confirm load order and look for some possible incompatibilities, that would help as well.
~Ramza