SharePoint and OneDrive keeping deleting files itself?

We use OneDrive and SharePoint. For some reason, OneDrive or SharePoint decide they going to delete files. My boss only had this problem one day where he had deleted 1000s of files. He blamed Avast but I looked and don’t see that Avast has anything to do with it. The files went in to the recycle bin. Is there any reason this is happening. He is saying that he didn’t delete anything and wasn’t in the building when it started. How can we stop this happening in the future?