Assume that you use the Report Viewer Web Part on a Microsoft SQL Server 2016 Reporting Services (SSRS 2016) report server that's configured to run in SharePoint integrated mode. In this situation, the Adjust height to fit zone setting of the Report Viewer Web Part isn't respected. For example, when you open the SharePoint webpage that contains the Report Viewer Web Part, only part of the report is showed up inside the Report Viewer Web Part. Then, if you refresh the webpage, more report content is displayed.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.