In similar cases it turned out most of times that either device was hacked (and only way out is netinstall it) or there was some mismatch between packages installed (and netinstall is the way out again).
Is there anything about failed upgrade in logs?
The preferred method of upgrading, though, is to run the semi-auto process on the device:
/system package update
check-for-updates
install
After reboot (which finishes the ROS upgrade process) you can upgrade also bootloader