CRS125-24G-1S hangs at "Starting Services"

We have several CRS125 units and two of them suddenly have frozen themselves at the “Starting Services” message on the router display. I’m not sure what could have prompted that but it could have been a power outage. Sometimes we have a lot of them.

Everything works fine again after doing a factory reset.

My question is if this is a known issue? Is it normal for routers to break like that after power outages? Should one invest in UPS so that the routers are always on even when there is a power outage? What else could have prompted the router to hang att “Staring Services”?