Recently getting ocassional blank system daily records in history

I have kept a log of each 30 day history log of my MPPT SmartSolar control for years to monitor the system performance. Now for no obvious reason I have begun to have blank days being displayed on some days in the history log on an unpredictable pattern. I have attached a recently taken photo.
Can someone explain why this has started to happen?

It is possible on those days the mppt did not start up. (Panel voltage not 5v above battery?)
Or a glitch in the smart network? Again the mppt did not start up?