Link to buildbot status page: https://uberchromegw.corp.google.com/i/chromium.perf/builders/Android%20Galaxy%20S5%20Perf%20(3)

It looks likes build23-b1 has two Galaxy S5s offline: 

32089d0db6a351b7, which failed with the following message: 

E    9.164s Main  Unable to reset USB for 32089d0db6a351b7.
Traceback (most recent call last):
  File "/b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/build/android/buildbot/bb_device_status_check.py", line 241, in RecoverDevices
    reset_usb.reset_android_usb(serial)
  File "/b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/third_party/catapult/devil/devil/utils/reset_usb.py", line 48, in reset_android_usb
    'Unable to determine bus or device for device %s' % serial)
DeviceUnreachableError: Unable to determine bus or device for device 32089d0db6a351b7
I    9.164s Main  Adding 32089d0db6a351b7 to blacklist /b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/out/bad_devices.json for reason: offline
I    9.182s TimeoutThread-1-for-MainThread  [host]> /b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/third_party/android_tools/sdk/platform-tools/adb devices -l





and 32082171745c5147, which failed with the following message: 

E    7.888s Main  Unable to reset USB for 32082171745c5147.
Traceback (most recent call last):
  File "/b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/build/android/buildbot/bb_device_status_check.py", line 241, in RecoverDevices
    reset_usb.reset_android_usb(serial)
  File "/b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/third_party/catapult/devil/devil/utils/reset_usb.py", line 45, in reset_android_usb
    reset_usb(bus, device)
  File "/b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/third_party/catapult/devil/devil/utils/reset_usb.py", line 29, in reset_usb
    fcntl.ioctl(usb_file, _USBDEVFS_RESET)
IOError: [Errno 19] No such device
I    7.888s Main  Adding 32082171745c5147 to blacklist /b/build/slave/Android_Galaxy_S5_Perf__3_/build/src/out/bad_devices.json for reason: usb_failure

Right now, this is causing Android Galaxy S5 Perf(3) to be down.

Infra-labs, do you know what might be causing this type of USB failure?