In ArcMap 10.4, the Raster to Polygon tool returns the error, "Error: 010067 - Error in executing grid expression" when the Raster to Polygon tool uses the Viewshed tool output as the raster input within a model.
Create two separate models to run the combination of Viewshed and Raster to Polygon.1. Create a new model.2. Drag Viewshed (Spatial Analyst) to the model.3. Add points and raster to Table of Contents.4. Set feature layers as the input for Viewshed tool > write output to disk.5. Validate > Run model.6. Create a new model .7. Drag Raster to Polygon in model.8. Add output of Viewshed to Table of Contents.9. Set Viewshed output feature layer as the input raster for Raster to Polygon tool > write output to disk.10. Validate > Run model.The tools work and produces the correct output when using this workflow.