I have installed all previous updates successfully.
KB3081424 gets to 35% and restarts. Normal so far. After the restart, it picks up where it left off and gets to 51%. Nothing suspicious.
As soon as it gets to 51%, BAM. We couldn't finish the updates. Then it starts rolling back, restarting itself around 5 times in the process.
When the PC was finally usable again, I went to the system event log and saw error 0x80070003, which means it couldn't find the update files that were supposed to be installed. Considering my first paragraph, is it possible that the update is not needed? If it is, please help me find a solution.
So far, I have found 5 other people on Reddit with the same issue.