After downloading the stage3 and the corresponding .hash.txt I ask sha256sum for a hash. After checking (manually unfortunately) I get different results for the locally produced hash and the hash downloaded from the server.
For now you can find my hash here: https://phamming.home.xs4all.nl/stage3-i686-funtoo-stable-2015-08-11.tar.xz.hash
I have not tested it with other stages from the same date, but both build.funtoo.org and ftp.osuosl.org have the same issue. 2015-08-08 from build.funtoo.org does produce the right sum.

p.s. I will remove this file as soon as the issue is resolved