Agentless Windows box randomly taking a base

I have a Windows machine that we are testing agentless backups on. The machine isn't doing anything to increase or change the disk size. It has taken a base 2 nights in a row. It took a large incremental the night before, then a base the night before that. Other nights it took an incremental of about 500MB which makes the most sense. 

The Events tab is not indicating any errors or any reason why the machine needed a base. I have called support about this issue in the past with no results. What can I do to figure this ouit?

Thanks