Here is my very sad story. I have a Macbook pro 13" retina early 2015 (MB 12,1). My bootrom version is MBP121.0167.B07 and according to this ( https://docs.google.com/spreadsheets/d/1qGRVF1aRokQgm_LuTsFUN2Knrh0Sd3Gp0ziC_VIWqoM/htmlview ) table I'm running a veeery old firmware, updated to yosemite.
I found this problem while I tried to upgrade to mojave (I'm runnig Sierra right now). Error while verifying the firmware. After many tries and repairs to the disk, I found the problem: my firmware.
So i tried many thing to update it. Install mojave on a external drive didn't help (same firmware error). I tried to boot with mojave using carbon clone (I cloned the hard drive from my girlfriend's macbook updated to mojave). I also tried to do a update while in mojave, but nothing.
I tried a fresh install of sierra, but no firmware updates. I tried to use El Capitan from a external drive, still nothing.
I tried some tool to install the firmware right from highsierra installer, nothing.
I tried to install it manually with bless command. The output was good, it sets the nvram to install the update after the reboot but nothing.
What should I do? Change the logic-board seems expensive and stupid if the problem is just a upgrade.