I have the same problem as you. My NAS model is 466c, and the system is Hero. When the NAS is turned off and then turned on again (not restarted), there is a high probability (almost every time) that it will fail to boot. The solution is to unplug the USB and plug it back in. The UPS provider has already replaced a UPS for me, but the problem still exists. He told me it should be a problem with the NAS, but QNAP told me it might be a problem with the UPS.