The problem was a changed patch file that was pulled from an external url by multimedia/x265. Due to the change the checksum did not match any more and the patch still isn't pulled into the quartely branch.
So to build all ports that require x265 from quarterly, one needs to cherry-pick commit 88c12b53a49ce5d7686cfcda9e2409ed3c1bd0f2 (or edit the distfile by hand / copy it from latest)
So to build all ports that require x265 from quarterly, one needs to cherry-pick commit 88c12b53a49ce5d7686cfcda9e2409ed3c1bd0f2 (or edit the distfile by hand / copy it from latest)