Probably true. I just had my S4 replaced because it would no longer charge one morning after I woke up. After inspecting the charging port and cable, there were

Probably true. I just had my S4 replaced because it would no longer charge one morning after I woke up. After inspecting the charging port and cable, there were clear burn marks. A few days before this is would randomly heat up and go into "cool down" mode or whatever they call it. This was with the stock battery and charger, so it was slightly concerning. I wouldn't completely rule out a genuine defect.