Storage Usage Report has been noticed as ZERO - Why ?

Hello,

Storage Report has been down and displaying ZERO statistics since last 1 week.Also it seems intermittent as per the below mentioned storage report graph.

And breakdown is as below :

Can anyone please let me know the reason - why this happened ? 

Note : I can see other reports as per the expectation such as Traffic and Search Reports,while Inventory reports are down at present.

As per the below link , I have checked data in reporting data table called WAInventoryAggregationByDatethat has reported ZERO data for the dates as mentioned in graph.

https://social.technet.microsoft.com/Forums/sharepoint/en-US/ab2302ac-8476-4e40-8fb6-b9bba4627815/storage-used-drops-to-zero

I have also checked timer job namedMicrosoft SharePoint Foundation Site Inventory Usage Collection thats not failed for last one month.

Would you please answer on following ?:

1. Would you please let me know what can be root cause for this ZERO report statistics ?
2. How to discover such failures more alertly ?
3. How to fix once noticed ?

Your help will be really highly appreciated.

Thank you in advance !

Kind Regards,

Dipti Chhatrapati