[Problem] AMI GLK laptop booting to recovery tab after boot logo replacement

Have a Geminilake (N3450) laptop with AMI Aptio UEFI and looking to customize the bootsplash for a customer. Tried using ChangeLogo.exe v4.5 and 5.0. Both successfully change the logo, but the laptop boots to the Recovery tab with the messages:

ROM Image is not loaded
ROM Image update denied

I can exit and boot normally with the new logo, but obviously that’s not workable for my customer. I’ve done the cursory searching here and elsewhere, and the only instances I’ve seen of similar issues are unresolved.

FWIW, I’m reading/writing the BIOS region of the flash using FPT from the EFI shell. The BIOS region isn’t protected in any way (bootguard, flockdown) but there’s some integrity checking being done by APTIO, which makes me think there’s likely a DXE that can be ripped out to resolve this