NanoPi R4S friendlywrt will do first boot, will not reboot

Steps:
-flash SD card with friendlywrt-5.15-20220125.img using dd
-insert card, power on, get to login screen -- all good
-reboot command given, unit powers down and up
-device hangs with the system led double-pulsing

I've tried with and without adding additional software on the first boot.
I've tried removing the root/setup.sh script
Nothing.
System can start the first time, won't on subsequent restarts.

Has anyone experienced this?