Yeah, one of my concern about the rather weak (and old) RK3288 chipset - even more so, for each additional added feature. I noticed serious issues when using the track skip << / >> buttons on my Live 4, pressing them repeatedly can cause the unit to temporarily freeze, same when skipping to long mix-tracks for >30min. The audio keeps on playing, but all LEDs (including the VU meters) stop for a moment, same for my connected DMX setup as I just learned.
That being said, I had no complete freeze or enforced power cycle yet, even during long 6hr sets - good! Still, I would have preferred more focus on stability, rather than fancy and highly demanding stuff like Stems.
And yes, a compact and nifty backup mixer is highly recommended (in general as DJ).