Is it possible that I need more Vcore with 1253 than with 1003?
I would say it's not likely that degradation took place, because last stable settings on 1003 where 48x100, 1.300V, max temperature 78°C. Now I need 1.320V for 4.8GHz.
I didn't touch any advanced settings on either BIOS, just raising Vcore was enough.