I'm testing the latest snapshot build on the NanoPi R4S (4gb) and have noticed that the reboot command is broken. The system doesn't come back up after issuing the command via SSH. Just as a sanity check, I've flashed a fresh card and attempted the reboot as the first command with the same result.
Image version: OpenWrt SNAPSHOT, r18400-f9782f5bcd from: (root) / snapshots / targets / rockchip / armv8 / friendlyarm_nanopi-r4s-ext4-sysupgrade.img.gz
Please let me know if there's any additional info that might be helpful.