title: ADB fingerprint command stuck
body: <p>Try first time:</p>
  
  <p><img src="https://i.stack.imgur.com/rsBpv.png" alt=""></p>
  
  <p>Try more than one time:</p>
  
  <p><img src="https://i.stack.imgur.com/LaNdW.png" alt=""></p>
  
  <p>I try to use <code>adb</code> command to activate the fingerprint scanner on my <code>Android</code> virtural machine - <code>Nexus5X</code>. The strange thing is: when I just execute <code>adb -s emulator-5554 emu finger touch 1</code> for one time, there is no response. But after I keep trying many times (as shown in the picture), it works on my <code>AVM</code>. It just seems that <code>adb</code> command was very unstable.</p>
  
  <p>Can anyone tell me what could probably be happening here?</p>