Windows Fast Ring builds keep sticking at 87% before updating. I got into a giant boot loop where the update would fail or I’d hard reboot (hold power button) and this was not working. This problem can be fixed by if computer is on WiFi, additionally plug it in via Ethernet. This may require a USB 3 to Ethernet adapter if your PC doesn’t have an Ethernet port.
- Unplug the Ethernet connector when Windows Update is stuck (for me it was at 87%)
- wait say 10 seconds, then plug in Ethernet again.
- upon plugging Ethernet in, Windows Update very rapidly finished the update and rebooted and continued installing Windows.
This happened for me on multiple Windows builds. Each time, the procedure above made Windows Update complete rapidly and successfully.