Game looks different after packaging

I thought I was finally finished with the lighting in the project I’m working on, it looked good in the editor, so I packaged it up and the final game looks completely different. What was a slightly lit wall is now completely black, and I get a strange jagged shadow when I turn on my stationary lights.

Why doesn’t it look like it did in the editor? What changes between the editor and packaged versions?

I’m also confused why there is no 64 bit shipping option in the standard release (I’ve heard you can only get it if you compile the GitHub version) - I can only build Debug and Development in 64-bit and I have 64-bit DLLs that I’m using, so why can’t I package to 64-bit?