I have Tab 4 T3310. I also had the same symptom. I fix it myself by prying open the case. Halfway through I accidentally corrected something, it turned on by itself. So I snapped it back in place. Initially, the plan is to replace the battery. Been a year now. The replacement battery still in its packaging. No sign of battery degradation. No clue what happen either. Some clunky dent and corner scratch remained as a testament of my atrocity. No plan to re-new casing.