Cooking and packaging catastrophically fails after upgrading from 4.14 to 4.15

Basically what the title states. I have a project I’ve been building for months now in 4.14. I upgraded to 4.15, bumped up my project to the newer version, and now I suddenly get so many errors I don’t know where to start. Project Settings have not been changed since 4.14, where they worked. I did add a bunch of stuff to the project, but I highly doubt that some new meshes and materials are what’s causing the issue.

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