Was that a chromiumos flashrom? or flashrom proper?

I didn't know there was a difference. The old flashrom was whatever John has on his website. The new one is compiled from source on the flashrom github, master branch..

Leaving a mix should be impossible if the firmware descriptor is cor-
rectly configured. Do you have a backup of the original descriptor?

I made a backup copy before I flashed the full rom but after I flashed the boot stub only and using the older version of flashrom from John's site. So I have something, but whether it is an accurate copy of the descriptor I can't say.

The important things is that it works now. Thanks Nico, John, and Haleigh for your help.