I've got this issue too, but i disassembled the phone n reassembled carefully to fix 1 of 3 issues i had n 1 worked but 2 needed software reinstallation. i think sometimes the phone does detect authenticity n as such gets a boot loop for incompatible screen type
just reinstall the mac os using external usb having os bootable or 1. turn off ur mac 2. power on while holding command and r keys simultaneously, this will boot ur mac in recovery mode 3. follow steps on screen and ensure are connected to the internet if that doesn't work replace HDD or connecting cables as d case may demand
actually, the digitizer is most definitely the issue. u may change the source u got the digitizers from. magnets have less effects on good digitizer as I've experienced. another thing is an exposed part of the home button flex, that causes malfunctions always