Using iframe in React to display local HTML file

I am trying to use an iframe in my React app to display a local HTML file. When I try to run my app (npm run start) it instead seems like the iframe is loading index.html recursively. It works fine when the source is an external URL.

Update: It works when deployed to Github Pages Update 2: Nevermind it randomly broke on Github Pages just now Update 3: here's the package.json

{
  "name": "wikiread-react",
  "version": "0.1.0",
  "homepage": "https://stationktkr.github.com/wikiread-react",
  "private": true,
  "dependencies": {
    "@testing-library/dom": "^10.4.1",
    "@testing-library/jest-dom": "^6.9.1",
    "@testing-library/react": "^16.3.2",
    "@testing-library/user-event": "^13.5.0",
    "react": "^19.2.3",
    "react-dom": "^19.2.3",
    "react-scripts": "5.0.1",
    "web-vitals": "^2.1.4"
  },
  "scripts": {
    "predeploy": "npm run build",
    "deploy": "gh-pages -d build",
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "devDependencies": {
    "bootstrap": "^5.3.8",
    "gh-pages": "^6.3.0",
    "react-bootstrap": "^2.10.10",
    "react-iframe": "^1.8.5",
    "react-tabs": "^6.1.0"
  }
}

App.js:

import './App.css';
function App() {
return (
<main>
<iframe title="test" src="altpages/test.html" width='500px' height='500px'></iframe>
</main>
);
}
export default App;

test.html:

<!DOCTYPE html>
<html>
<body>
<h1>Test 1</h1>
</body>
</html>

This is my file structure:

project structure ]

Here's what I get if I load "altpages/test.html" directly in the browser (what I would expect):

enter image description here

Opposed to what I see when I run "npm run start" from the terminal (in the wikiread-react folder):

enter image description here

Using the inspector, you can see that it is a series of nested iframes:

enter image description here