Syspugrade fails, no hw ID, Archer C7

Trying to flash today's build onto several different Archer C7s here and it's failing on all, apparently because the current hardware ID is coming back as the empty string. Anyone seeing this, or have seen it in the past?

jeff@devel:~$ sysupgrade /tmp/openwrt-build-2018-04-15-0950-ar71xx-generic-archer-c7-v2-squashfs-sysupgrade.bin 
Image metadata not found
Invalid image, hardware ID mismatch, hw:  image:c7000002 00000001.
Image check 'platform_check_image' failed.
jeff@devel:~$ . /lib/upgrade/ 
jeff@devel:~$ . /lib/upgrade/ 
jeff@devel:~$ tplink_get_hwid

Trying sysupgrade -F fails with Command failed: Not found and tracing it as it is executed reveals

+ ubus call system sysupgrade '{
		"prefix": "/tmp/root",
		"path": "/tmp/openwrt-build-2018-04-15-0950-ar71xx-generic-archer-c7-v2-squashfs-sysupgrade.bin",
		"command": ". /lib/; include /lib/upgrade; do_upgrade_stage2"
Command failed: Not found

Looks like it is defined

jeff@devel:~$ fgrep -r do_upgrade_stage2 /lib
/lib/upgrade/ {

I'm assuming this is a problem with the previous build (the one that is presently flashed, and unable to upgrade), probably on 2018-04-08


(Identifying merge base if you're not on master)