Yeah I thought about plain text but I couldn't do that because I would have lost too much other important formatting. It's not my document, I'm helping someone out with this. I tried the various paste options too.

In the end, for whatever reason, Word was showing all of those sections but they weren't actually there. I've never seen that before. After closing and opening the document the sections were gone (one of the numerous things I did must have worked, I just can't believe the sections were still showing).

Anyway for future reference if anyone runs into this very whacky issue, try completely closing out of all Word windows and signing back in. Sometimes it's the simplest solution haha...