WinPE won't boot on Extreme 3.0 but does on several others

I’ve created USBs to boot WinPE for years and upgraded to 4.0 nine months ago. My steps for creating a bootable USB are reduced to:

  • clean

  • format

  • make active

  • copy WinPE files

  • set bcd

Works everytime on at least eight other brands I’ve used.  The SanDisk Extreme USB 3.0 doesn’t and I have two of them.  For those that work with WinPE you may have seen the “:)” with a message that flashes by quickly when the boot setup or files aren’t correct. I’ve tried diskpart “clean all” instead of just “clean”. Diskpart “details” shows everything fine.

WinPE 4.0 (6.2)

Any ideas on how to fix or debug this issue?

Never really tried this myself. But have you tried doing this using PowerISO?