I'm not 100% sure, but more like 95%
sure that its dashlaunch patches that is causing your problems.
I remember having the same problem last year, then only bad thing is I can't remember exactly what I did lol.
I do remember it having something to do with renaming the dashlaunch patches eg Falcon one to zephyr. Then applying it manually, but I suppose you could do this before building an image in bestpig?
I don't have my zephyr anymore so cannot do any testing for you on the machine itself but I still have the nand dumps. It was the exact same type of system as you have there, a Zephyr M$ Refurb, Jtag'd as a falcon with aud_clamp wiring.
I'd probable try using Team Xecuters Jrunner application, then just build the latest dash 15574 but instead of using your original nand dump use your last good JTAG dash dump. I just tried it with my old Zephyrs dumps and this is the only way it would build a valid image.
Pics showing what to do below, open your nand paste cpukey, select the settings circled (You will probs have to download the 15574 dash files if you've not used the program before), then click create image. The bottom pick is the created image opened up in jrunner to verify ifs good/valid, numbers in the circle 2bl-7bl should be the same as the picture.
Unfortunately your going to have to flash this new image manually.
Good luck mate