A previous incidence of this was reported here: https://community.amd.com/message/2832835#comment-2832835
As has been found by users in that question's thread after it was marked answered, it's happening again. The symptoms are the same.
It affects all the tar.xz archives linked to on: AMDGPU-PRO Driver for Linux® Release Notes
I've downloaded the files multiple times to make sure it was not caused by a network fluke.
The output of cksum, ran on any of the files I've downloaded, is consistent, and is the different from what was reported in the earlier incidence:
3138088028 172919408 amdgpu-pro-17.40-492261.tar.xz