When I discovered that my SL 16.4.2 only had 4 outputs working, Sub 1,2 Aux 5,6, all others were dead or like CR and headphone crackling (not sure of the circumstances when this started because I used S/PDIF output for the monitor and headphone amp, so the problem remained hidden) I found a number of KB articles suggesting that a Firmware Restore may fix this type of glitch. Page "FireStudio Interfaces Force firmware update with Universal Control 1.7.x" advises to hold "CTRL+ALT and then click on Check Firmware", which will "force the update to run." despite device firmware being up to date. I've attached a capture of a dialogue box offering installation of a 'factory test mode', which is what happens holding the Alt key (Ctrl seems irrelevant) while clicking on 'Check Firmware' in both 1.7.6 and 1.7.2 UC. Clicking YES appeared to make sense to diagnose the fault and cancelling aborts without restoring, unlike what is claimed by KB instructions.
At the end of the flashing process all buttons on the control panel were fully illuminated and can be dimmed by pressing, faders, knobs and continuous encoders change various level meters and the monitor section encoder switches through segments of the channel LED display. The LCD only shows one seemingly fixed digit 0.
Given that StudioLive 16.4.2. is EOS, the support people don't seem to be able to advise me if and what is the way out of the dreaded 'factory test mode', or indeed confirm that such a function exists, which amounts to the old trusty unit being effectively BRICKED!!!
Is there any other way to 'reset' the device out of this "factory test mode"? Upgrading regular firmware 1.50a, build 190 with UC 1.7.6 and 1.7.2 completes successfully but nothing changes. This is now possible without the (seemingly phony) workaround to "force update to run" holding the 'Alt' key, in effect, UC detects another version despite repeated flashing ending in completed OK. Similarly, Factory Rest runs as expected, but doesn't change anything.