Uiautomatorviewer Location Of File "error Obtaining Ui Hierachy"

I played around in uiautomatorviewer with the most left and most right button, if I can save something here It seams I was able to specify a file here, but now it disclaims about

Solution 1:

After investigation a lot (included the source code at https://android.googlesource.com/platform/frameworks/testing/+/aecdc4a/uiautomator/utils/uiautomatorviewer/src/com/android/uiautomator)

A simple reboot made it work again !