I had been using May's Win10_1511_1_EnglishInternational_x64 ISO from TechBench, but I can't use WR to integrate KB3156421 without the image corrupting, but it works fine if I use the official windows download tool to get equivalent English GB/International ISO (which doesn't have the prebuilt .wim... which kills my computer the first time I mount it).

After installing the TechBench windows Windows Update also fails to install it!

Anyway, there's no bug in WR, I believe it's a TechBench ISO bug, just though y'all should know