I've left out some code I felt irrelevant to this post but I will add the rest if anyone wants me to.
My problem comes after I run vapor deploy production, I see that a chunk has failed to load in my browser console, and when inspecting the network tab I can see that see that it has tried /undefined/js/0.js - suggesting that ASSET_URL is undefined.
Has anyone else had this problem? Any help would be greatly appreciated.