Issues restoring phone after battery replacement

After replacing the battery in my 1st Gen iPhone SE, it kept just showing the Apple logo and rebooting continuously from there. Hard resets made no difference, but eventually the phone showed the screen asking to be restored, and stays on this screen for however long I leave it there. However, upon every attempt to restore it it immediately reboots as soon as the spinning wheel under the Apple logo appears and the restore fails with a 4013 error. I've taken the phone back apart a couple of times and checked all connections and nothing appears to be loose or misseated. What could be the problem?