I had this exact problem this week. I know what caused it for me. I used Tweakgeek to delete de External drive app on my Nexus 5 because there is no SD slot on the Nexus 5 and I didn't want to see the icon anymore.
My phone started to overheat and use battery like crazy. I restarted the phone and there was no more network indicator like in your screenshots. Also, for some reason all my unused space started to fill up (with error logs I bet).
I updated from the legacy channel to OTA 1 and it didn't resolve the problem. I flashed the phone to OTA 1 and now it's resolved.