At least with first generation Qi devices I think it was the device and not the charger to blame. I have a branded Lg charger and my Nexus 4 would occasionally

At least with first generation Qi devices I think it was the device and not the charger to blame. I have a branded Lg charger and my Nexus 4 would occasionally overhead on it depending on how it was positioned. I eventually abandoned it and gave it to my wife who used her Nexus 5 with it for years and never complained of overheating.