Nikon Asia has published a video about testing Nikon D850 DSLR camera at a very extreme conditions. From the result, we can that Nikon D850 DSLR camera is very reliable. Nikon D850 camera is still out of stock in most US stores. You can pre-order now at Amazon, B&H, Adorama.
From Nikon Asia:
Watch how the Nikon D850 is verified by strict reliability tests to offer high resolution, high-speed performance and versatile functions. From conducting drop, impact and vibration tests, to simulating temperatures and humidity levels far beyond the operating range, the D850 has proven its durability in harsh and extreme weather conditions.