It most certainly looks like corrupt BIOS but I fail to understand if it is so corrupt then how does it function to boot Windows.
Please remove all but one RAM and have that in the first position in the first slot.
Your manual says DMM1 is the one closest to the CPU.
Then try to enter BIOS.
If not successful then change that RAM for new and if not successful then move the RAM to the second DMM2 and try.
I have seen faulty RAM do similar things to this before.