Chosen Solution
I took the battery out of 2 of my iPhone SE’s to replace the powerbutton/volumebutton etc. everything did go nice and smooth as usually. But now they are BOTH in bootloop. I can’t think of any cause.. the only thing I can think of is that I bent the battery’s a bit, because both of the adhesive let loose :(. Could this be my cause? Because then i will just get some new battery’s.
The battery will work fine, even when bent. Severe bands can cause fires, but gentle bends can be flattened out again. Either your motherboard has a problem, or your power button is stuck. Try with the switch connections disconnected, and connect the phone (off) to your computer running iTunes. It should boot normally, I test motherboards out of case this way.
