i have same problem but different gpu series.

techpowerup website only provide 256KB bios,
our bios is 512KB size.

although same gpu, same codes, same memory type, when we download bios from techpowerup and programmed it to our gpu using amdvbflash, it will brick our cards.

you can compare, download your bios with amdvbflash and download in techpowerup bios collection website