steps to reproduce issue

• run npm install
• run npm run dev
• observe that there is a plugin startup message starting example sandbox plugin
• press ctl + c to quit the process
• observe that there is no plugin stopped message
• go into your node_modules to node_modules/@remix-run/dev/dist/devServer_unstable/index.js
• change line 139 so that instead of having stdio: "pipe" you have it broken into two lines, one for stdout: "pipe" and one for stdin:"inherit" like so:

let newAppServer = execa__default["default"].command(cmd, {
   stdout: "pipe",
   stdin: "inherit",
   env: {
      NODE_ENV: "development",
      PATH: bin + (process.platform === "win32" ? ";" : ":") + process.env.PATH,
      REMIX_DEV_ORIGIN: options.REMIX_DEV_ORIGIN.href,
      FORCE_COLOR: process.env.NO_COLOR === undefined ? "1" : "0"
   },
   // https://github.com/sindresorhus/execa/issues/433
   windowsHide: false
   })

• re-run npm run dev
• again you should see the plugin start message starting example sandbox plugin
• again press ctl + c to quit the process
• observe that now you see the plugin stop with stopping example sandbox plugin
• observe that the process hangs until you press ctl + c again.