RN314 starts to boot then gets message Mount_Block_root+25e

And if you disconnect power and then re-conect, it boots fine?

I've seen a similar display caused because the power-off circuit doesn't funtion properly.  If it did, the NAS would re-boot and you'd never see it because the NAS wouldn't get to that point.  If that is what's happening, it's usually an indication that the internal voltage converter for the 3.3V Standby (3.3VSB) power (which powers the on/off and the NIC circuits) is failing, and there is no solution other than putting up with it.  But it will likely get worse and you may lose communications with the NAS because the NIC isn't getting the right voltage or it may not turn on.  Unfortunatley, while the NAS monitors the normal 3.3V, I see no indication in the configuration file that it can monitor the 3.3VSB.  The 3.3VSB is always on, even when the NAS is "off", and then it's running without the fan running.  If the NAS is allowed to get to warm when off, this can be the result.

It could be, however, that something else in the power-off sequence is crashing, so you should check the downloaded logs and see if anything seems amiss.  Others on the forum can help you better than I in interpreting them.