Announcing Windows 10 Insider Preview Build 21301

(For some reason I was asked to register on the community, that's why my username changed)
So...
- I get informed that I must restart to update and I do
- The laptop restarts a couple of times and shows progress
- At a certain point, it tells me that it is undoing the changes
- Restarts and, on the Windows Update Settings, 21301 is available
- Rinse and repeat. Several times.
I'm repeating right now to see if I can get more info.

- Configuring Updates: 100%

- Working on Updates: 25%, restart, 48%

- Got a message about the Windows Insider Build running into a problem

- Restarts, "undoing changes"

On Windows Update:

Error 0xc1900101

And, yes, I followed all steps suggested by that type of error. I've space, disk checked, device manager checked etc etc