ArcGIS Pro 2.9.x Microsoft .NET Bug
Recent Microsoft .NET Update Resulting in ArcGIS Pro 2.8 and 2.9 Crash When Changing Symbology
Recent Microsoft cumulative updates result in a crash for ArcGIS Pro 2.8.x and 2.9.x users when changing symbology. For more information about the crash and what Esri recommends that customers do, see https://community.esri.com/t5/arcgis-pro-documents/recent-microsoft-net-update-resulting-in-arcgis/ta-p/1221829.
The issue can be fixed by upgrading to ArcGIS 3.0, or by patching ArcGIS Pro to 2.9.5. The official CSUMB version of ArcGIS Pro is 2.9.x.
To fix the issue and remain with the official CSUMB version of ArcGIS Pro, please download and install the Esri ArcGIS Pro 2.9.5 patch.