Motherboard Heats Up with Only Battery Connected (HTC U11)

I've just attempted a screen repair on my HTC U11. I tested the new screen working before starting final reassembly. Once the screen was reassembled, and before closing everything up, I noticed the motherboard power circuit heats up considerably when the battery is plugged in. To make matters worse, the phone doesn't power on anymore like it did in testing. I isolated everything to just the motherboard and battery by removing the motherboard from the case completely and disconnecting all cables, including the front and rear camera. Plugging in the battery still results in heat from the motherboard, very close to the battery. I can touch with my finger, but gets uncomfortable after a minute or so. My question is this: what should be expected for heat with just a motherboard and battery? Should I expect a little or none at all. I'm assuming I have a short somewhere, but trying to figure out where things are going wrong that I can't turn on the phone. Any suggestions? Thanks in advance!