First WU attempt failed with a typical indecipherable 0x8024200D error. Apparently it requires downloading the update completely again. Yay 2nd time was a charm
But of course you captured the ESD and created an ISO first time around, so that won't matter..... right?
Well, this can be used to "switch" to Anniversary Update from 7/8 directly. Almost RTM build. I think it will continue to receive updates and fixes.
Remember that the real RTM or whatever it can be named is released to the Slow Ring too so we need to wait and see wich is the real one.