Webpack.mix.js question

Hi Just updated my site to v8.xxx laravel and I have a question about the updated webpack. Previously in package.json i had the following custom npm run script

        "prod": "npm run production",
        "production": "mix --production",
        "production-upload-s3": "cross-env NODE_ENV=production UPLOAD_S3=true node_modules/webpack/bin/webpack.js --config=node_modules/laravel-mix/setup/webpack.config.js"

However when i run npn run production-upload-s3 or any other production command ie npm run production, mix --production etc it starts deploying the assets to S3. Is there any documentation as to how to set up a custom npm script or shed any light on this issue. Or is it a case that i need to add ENV=production UPLOAD_S3=false to the standard npn run scripts? The version of mix I believe is "laravel-mix": "^6.0.27" so possibly may have to downgrade as the older version seem to work ok

if (mix.inProduction() && process.env.UPLOAD_S3) {
    webpackPlugins = [
        new S3Plugin({
            logger: console,
            include: /.*\.(css|js|svg|fonts|png|ico|json|map|jpg|jpeg)$/,
            s3Options: {
                accessKeyId: process.env.AWS_ACCESS_KEY_ID,
                secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
                region: process.env.AWS_DEFAULT_REGION,
                httpOptions: {
                    timeout: 240000,
                    connectTimeout: 240000
                }
            },
            s3UploadOptions: {
                Bucket: process.env.AWS_BUCKET,
                CacheControl: 'public, max-age=15552000, immutable'
            },
            basePath: '/',
            directory: 'public_html'
        })
    ]
}