Phone keeps overheating and powering off?

I have replaced the back glass, the screen and battery. First battery was overheating and thought it could have been defective from Amazon, they RMA'd it and the 2nd one did the same. Ordered one from iFixit and it was good for a couple weeks then started overheating again and will shut down from the temp. Is there a way to determine if the charging port is fault, a bad battery connection, or something else (likely not the cable/AC adapter as I have the same issue with multiple). Running iOS 18.