I would loosen the memory timings a bit and see if that resolves the ECC errors. x265 performance shouldn't fall since it generally benefits more from memory clock rate than latency.
Also, could you share some relevant info about your processor, mainboard, and UEFI? I see many internet commenters question whether their ECC is working (or ask if a particular setup would work), and far fewer that report a successful ECC consumer desktop build. So it would be nice to know some specific product combinations that really work.
Also, could you share some relevant info about your processor, mainboard, and UEFI? I see many internet commenters question whether their ECC is working (or ask if a particular setup would work), and far fewer that report a successful ECC consumer desktop build. So it would be nice to know some specific product combinations that really work.