Battery overheating despite replacement

Battery overheats to around 68 C then device shuts down. Power saver does not work. I installed a custom ROM (Lineage OS 14.1) and that seems to work, it functions like a normal phone except I can't play games for long periods. Idle temps on custom ROM and set to battery saver sit L's around 42-45 C. I have tried replacing the old battery (Anker 3220mAp) with another anker battery but still the same problem. Could the sensor on the motherboard be dead or damaged? As when it says temps are 66C the phone does not feel hot at all. Even when removing the back cover to feel battery, it does not feel hot. Any ideas?