Windows 10 2004 and 20H2 had an error that caused chkdsk to simply corrupt disk file systems.
These are the updates that fix the scary bug
Many of us have run chkdsk in the terminal window when we think there are problems with the file system, but that the tool that should analyze and perhaps correct errors, creates major errors, it is something new.
Do not run the "chkdsk / f" command (especially not on C :) if you have one of the updates below:
Microsoft reveals that the errors can be found in the updates KB4592438 (2004) and KB4586853 (20H2).
This is how Microsoft explains the gross error
"A small group of devices that had this update installed has reported that running chkdsk / f may corrupt the file system and the device may not start."
The problem should now be fixed according to Microsoft, and if this has happened to you, the error correction is actually to run chkdsk again, but from the recovery before Windows (does not) start (ie: do this only if Windows does not start):
The device will probably start in the Recovery Console, if not start this