People will tell you “I don’t have these problems, so they don’t exist”. But let me tell you… I encounter a lot of your problems consistently and I knew it was only a matter of time before more people encountered them as well. The more people find out about these products, the more these issues will raise concern.
I consistently encounter these same problems you have described: needing to restart the players due to glitching, the (!) quality stream mismatch, LAN issues (this happens frequently), touch screen lag, and instant doubles issue (this happens A LOT).
Here is a link to a lot of my main issues, however, every issue I’ve encountered is not listed here - Massive List of SC5000 Issues (all with video evidence)
EDIT: To me, these issues aren’t common with most people because they don’t use their units for 8+ hours at a time. When I DJ’d a recent wedding, the units were on for 10 hours and I could list a handful of issues I encountered by the end of the night. Additionally, I’m convinced most people aren’t sporadically mixing with all 4 decks, for hours on end, super quick. I believe these factors contribute to a lot of these issues; the long term hardcore mixing on them is where these issues shine.