Cannot paint textures onto terrain, errors are raised

When loading more than one texture into the texture painting tool and attempting to use it on the terrain, nothing is painted and the following error is raised many hundred times.

Exception: Float array size wrong (layers should be 3) UnityEngine.TerrainData.SetAlphamaps (Int32 x, Int32 y, System.Single[,,] map) (at C:/buildslave/unity/build/artifacts/generated/common/modules/Terrain/TerrainDataBindings.gen.cs:656) UnityEditor.SplatPainter.Paint (Single xCenterNormalized, Single yCenterNormalized, Int32 splatIndex) (at C:/buildslave/unity/build/Editor/Mono/TerrainEditor/TerrainInspector.cs:121) UnityEditor.TerrainInspector.OnSceneGUICallback (UnityEditor.SceneView sceneView) (at C:/buildslave/unity/build/Editor/Mono/TerrainEditor/TerrainInspector.cs:1892) UnityEditor.SceneView.CallOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2397) UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1715) UnityEditor.SceneView.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1585) System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)

Upon further research of this error it is stated that this is a problem that has been reproduced in my version of unity and has been "fixed" clearly not. it also says that there is a workaround however that workaround is not documented on that page.

Does anyone know why this is getting raised and or how to fix it?