npm run build makes build/, complains it already exists - reactjs

Question

I'm building an ASP.NET Core app with React in Visual Studio. When I run npm run build, I get the following error:
Creating an optimized production build...
Failed to compile.
EEXIST: file already exists, mkdir 'G:\My Drive\[redacted]\ClientApp]\build\static\js'
I've deleted the build folder and run again, but it creates it and then complains again that it already exists.
Here's my package.json:
"name": "partssearchtool",
"version": "0.1.0",
"private": true,
"dependencies": {
"#emotion/react": "^11.7.1",
"#emotion/styled": "^11.6.0",
"#mui/icons-material": "^5.3.1",
"#mui/material": "^5.4.0",
"bootstrap": "^4.1.3",
"chart.js": "^3.6.0",
"jquery": "^3.4.1",
"merge": "^1.2.1",
"oidc-client": "^1.9.0",
"react": "^17.0.2",
"react-chartjs-2": "^4.0.0",
"react-dom": "17.0.2",
"react-router-bootstrap": "^0.25.0",
"react-router-dom": "^5.1.2",
"react-scripts": "^3.4.1",
"reactstrap": "^8.4.1",
"recharts": "^2.1.6",
"rimraf": "^2.6.2",
"synp": "^1.9.9"
},
"devDependencies": {
"ajv": "^6.9.1",
"cross-env": "^5.2.0",
"eslint": "^6.8.0",
"eslint-config-react-app": "^5.2.0",
"eslint-plugin-flowtype": "^4.6.0",
"eslint-plugin-import": "^2.20.1",
"eslint-plugin-jsx-a11y": "^6.2.3",
"eslint-plugin-react": "^7.18.3",
"nan": "^2.14.1",
"typescript": "^3.7.5"
},
"eslintConfig": {
"extends": "react-app"
},
"scripts": {
"start": "rimraf ./build && react-scripts start",
"build": "react-scripts build",
"test": "cross-env CI=true react-scripts test --env=jsdom",
"eject": "react-scripts eject",
"lint": "eslint ./src/"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
}
}