I've been experimenting with the QLC+ on Raspberry Pi 3B+ and noticed that the QLC Blackout button has no visible affect on the Fixture Monitor window (as viewed via HDMI display), However the actual DMX output is blacked-out. On the PC I'm used to the Fixture Monitor being a reasonably accurate representation of the DMX electrical output.
This affects QLC image 20181110 v4.12.0. Note the previous image 20180410 v4.11.2 works OK.