Sysupgrade ignored on RPi CM4

I'm currently runnining 21.02.2 on a CM4 with the Seeed router board. Openwrt was originally installed from my own build using a factory ext4 image.

I'm trying to upgrade to 21.03.0-rc4 using the sysupgrade process/image. The file uploads fine, checksum is good, and the process seems to go forward. However, upon reboot, I'm still running 21.02.2.

So, looking for suggestions on how to figure this out or what may be wrong.