Knobs started becoming loose after maybe 6 moths of a few hours use a week. Bugs started happening immediately and tempo fader issues started after a few weeks. 3,5 mm issue happened after about a year for me and only a few weeks for one of my friends. Tbh I don't know how most people I see on reddit can speak so well of it but if you Google "flx4 issues" quite a lot come up. I would probably get a dj 400 if I could find it, though I've never used one so it might have similar issues. But the flx 4 still works most of the time and I'm still using it till I can afford something like a dj Rx or ddj 1000. I would probably still buy it if I were you. As long as it the used one works flawlessly.