OK my view is this ...
You have never reflashed the chip therefore it has Evox M8 16 on it now and this bios works 100% perfect on xbox 1.6 with samsung ram. So a reflash probly wont help alot but sure you can do this to rule that out.
I would suggest formatting the hard drive as it may contain some errors like cross linked files , fat problems , bad sectors etc that are playing havic !
HackDaBox !