OK, I've reflashed the main & diags kernels, reflashed the diags partition, and have access to diags once more. The first diags boot reformatted the /var/local partition as part of the boot process. I essentially followed the instructions in
the new eMMC thread minus the uboot portions - everything checked out. Upon loading update_kindle_5.4.3.2.bin (which flashes successfully) and rebooting into main, it's once again sitting at the "spinner". What should I do next?