For anyone who has this same issue in the future: I was using duckstation (newest version), and what I thought was the newest version of the beta branch. Every time I used Defend with any character the game would freeze. I searched to see if anyone else had this bug but the only posts were apparently due to using a different emulator, and fixed when they switched to Duckstation.
Stumped, I did a fresh reinstall of Duckstation, and a new download of the FFT rom and the Remix mod, and started a new save. Same issue.
Then I realized the download links at the bottom of the post only go to 1.2.16, and the newest version was 1.2.30. The download link for the newest version is right at the beginning of the post. Downloaded that, started a new game, and the problem's fixed.
EDIT: The first reply to the thread also has the newest versions. If you're dumb like me, you're welcome.
Stumped, I did a fresh reinstall of Duckstation, and a new download of the FFT rom and the Remix mod, and started a new save. Same issue.
Then I realized the download links at the bottom of the post only go to 1.2.16, and the newest version was 1.2.30. The download link for the newest version is right at the beginning of the post. Downloaded that, started a new game, and the problem's fixed.
EDIT: The first reply to the thread also has the newest versions. If you're dumb like me, you're welcome.