Just like everyone releasing 1809 I will fail to update until today.
It will freeze in BIOS exactly.
Even clean installation will freeze in BIOS.
Incidentally, updating from 1607 to 1703 and 1709 also failed. At that time, I solved it with a clean installation, but this time it seems not to be successful.
CPU: i7-6850K
MB: MSI X99A XPOWER GAMING TITANIUM (BIOS.ver 7A21v15)
GPU: GTX 1080
SSD: Samsung 960 EVO 500GB
OS: Windows 10 Pro 64bit 1806