This issue is not reproducible with ArcGIS Pro 3.6. The test was conducted on a small disk volume mostly filled with larger projects. When the remaining space on the volume is very small and a large map is added, causing the updated project to exceed the available space, the following error message is returned when clicking Save: "Failed to save LargeProject to F:\LargeProject.aprx." When saving the project to another location and attempting to save the project back to the small disk volume using Save As, the same error message is returned. ArcGIS Pro 3.6 did not crash during any attempt to save the project to the small disk volume.