After battery replacement, terrible performance and overheating.

I replaced my iPhone SE 2020 battery and followed the ifixit guide, and now it gets hot and has a terrible performance drop. I have tried factory resetting and unplugging and repluging every connector on the phone (even ones I didn’t touch during the replacement). Here are some 3DMark scores:

Latest is the one I just took and as you could see, it is abysmal compared to the average:

Edit: on a cold boot it runs as expected but after a few minutes it heats up and throttles.

Edit 2: Coconutbattery