What validation does Windows 10 bootloader perform on the ESP

I can boot Windows 10 by running EFI\Microsoft\Boot\bootmgfw.efi on the ESP (2nd hard disk partition). However, if I copy the EFI folder to a 100 MiB FAT32 file system on another disk and attempt to boot from there, I get the startup repair screen within a second or two. The error code listed is 0xc000000e. I know the contents of this other disk are correct because if I copy it to a usb stick, I can boot from the usb stick. Clearly, there's something about the disk itself and/or its file system that causes Windows to error out with 0xc000000e.

The only constraints I've seen on the ESP used for Windows boot is that it must be FAT32 and must be at least 100 MB: mine is both. Are there any other checks performed by the loader, which could result in the error code mentioned?

Thanks, Brett S.