Let me start by saying 2 things. First, the Souncdscape system is fantastic. I used to teach audio, have a long background in live and studio engineering, and I researched a lot before committing a lot of Money - 2 x L3S , 3 x L3M, 3 x L2M and the m20 mixer. I love the rig .
second, I get frustrated with posts from users who clearly lack the knowledge required to understand equipment of this type, and who don't read the manual. Time and time again there are crazy complaints that are not the fault of the gear but the fault of a user who has not taken the time to learn how it works etc.
I think companies like line 6 cope very well with this frustration and remain polite etc........
I also understand the liability that a company faces if it publicly acknowledges a problem and realise that this is a decision that cannot be taken lightly.
Not withstanding the various responses I have seen to the volume drop issue are troubling.
My M20 exhibits this fault on a regular basis, on both jacks and xlrs and on multiple channels. Thank God it has not yet happened at a gig. Replugging the input usually clears the problem.
On my guitar input ( HD500X going direct) the fault shows up in 1 or other of the stereo linked inputs . The difference in level is clearly visible on the channel meter and the master meter. At my last rehearsal the fault exhibited on a vocal channel as soon as it was plugged in......then cleared on replugging.
The gain drop looks to be 12 dB or so...enough that it sounds like its one speaker only at first.
As my guitar rig runs direct I use the M20 every day. When I get back from rehearsal it gets set up and remains so for a week - unless there's a gig in between. During that week I may have the level drop once or twice on average over 8 - 12 hours of use.
whether this is hardware or software is hard to judge ....but the fault is real.
If acknowledged us users could at least see a future where this might get sorted. I remain a fan and advocate of the system. I just want it to be reliable.