Did u try hard resetting? I had issues on build 10572 trying to get the newest build and it was stuck on 21% for 6 hours after a hard reset it let me update
answers dot microsoft dot com slash en-us/insider/forum/insider_wintp-insider_install/error-0x80070538-trying-to-install-build-10581/d6b7a3af-c202-4d4f-85e9-4c59f6323064
answers dot microsoft dot com slash en-us/insider/forum/insider_wintp-insider_install/error-0x80070538-trying-to-install-build-10581/d6b7a3af-c202-4d4f-85e9-4c59f6323064
Yeah, I saw that, and they suggest rolling back to 8/8.1. Umm... I might this weekend. But it's a pain. This is beta, but having an upgrade path should be one of the first things you get worked out.