Cannot partition w/ Boot Camp Assistant on macOS Mojave Late 2016 Macbook Pro running Mojave 10.14.3, APFS-formatted (ugh).

I have run Disk Utility to verify my disk, and I've run fsck -fy from single-user mode several times. Both of these have reported absolutely no errors.

And yet, whenever I try to run Boot Camp Assistant to dual-boot with Windows 10, I get an error that says: "An error occurred while partitioning the disk."

Thinking I'd be clever, I also tried to create a partition manually through Disk Utility, but that didn't work either. I also reinstalled macOS in Recovery Mode.

I am starting to suspect that this is a problem with APFS. What other commands could I run to receive more information as to why Boot Camp Assistant won't let me create a partition to run Windows? Thanks in advance.
The secret trick was running fsck_apfs -o -y. ‍♂️