I have a report with a SharePoint Online folder containing CSV files as data source, around 20 at the moment, each containing 4-800k rows. In the report there's a visual showing the number of rows for each month, but the number is incorrect for some of the months showing less than there actually is. It's not a filtering problem, I even recreated the visual from scratch, the issue remains. What makes it strange is that the months where the numbers are incorrect, and even the numbers changes from time to time without touching the source or the PBI file. Last week February and May was incorrect, yesterday it was February and March, before that, June, today it's February and May again, but with different numbers than last week. But every time it's less than the actual, never more.
My idea was that a strange character hidden somewhere in the source causes it to misread some rows, but that doesn't explain why the numbers change. Any idea? Have you experienced something like this before?
Please test to load data from this SharePoint Online folder which containing CSV files into Excel, if it still misread some rows, the problem is on the data source side, instead of Power BI. You should check those .CSV files.