RS4D just suddenly dropped off line

My RS4D just suddenly dropped off the networks. Can you read the TAR log and tell me what the error was. One of my router networks also disconnected momentarily when this happened. No power surges occurred. Routers and the RS4D are on a UPS. I rebooted it with a power off / pause / power on sequence. All came up okay / normal.
Would like to know what caused the drop off. Any ideas? (Could it be a faulty UPS?)

Here is the TAR file I forgot to attach:
RSH.R29F6.2021-05-16T20_32_21.logs.tar (4.2 MB)

Hello Gary,

Thank you for your report and for your logs. From them, nothing appears out of place, and everything is working as it should.

Your Shake is now visible again on our StationView portal, here: RS StationView