I was just getting a level on a virtual instrument and had it outputted to builtin audio1. While I could still hear the VSTi, I changed to another output. The VU meter still shows a signal on audio 1.
Is metro leaving the display of audio 1 as it last saw it?
below is a snippet of the effects window on top of the mixer.
If I now play the VSTi on audio 2, the level at audio 1 remains.
(obviously the fix is to wait a few moments for the level to drop before switching )