(1) On older Mackie VLZ mixers (all I can attest to), the channel fader/slider, if left in one position/setting, would slowly break contact because that spongy/squishsy padding beneath the slider would somehow settle. It drove us crazy for months with tech visits. Move your sliders back to zero when you're done with your sessions. I don't know if this was ever addressed by Mackie---it put us on the Allen-Heath route (absolutely no regrets since).
(2) The internal ribbon connectors are notorious for separating and/or failing in the older VLZ mixers. Not that it happened to all or a lot of them (I don't know), but I'd be willing to bet it's the first thing that the tech is going to suspect. It was the first thing they always brought up to me.
I get the impression that the SRMv2 speakers (the Class-D stuff) is not as well received as the original versions. I did have two SRM150 speakers fail on me---one within an hour (returned & replaced) and the other after about 8 hours (returned). Never got a third one.
Paj
8^)