EditorGUI.Popup drawing in the wrong position (ONLY ON MAC)

Hope somebody can help with this weird problem,

I am drawing a popup menu in the editor from a custom property drawer, on PC the popup draws exactly as expected, however on a mac the popup is drawn right at the top of the window as shown in the image.

the code:

 [CustomPropertyDrawer(typeof(SoundSelector))]
 public class SoundSelectorDrawer : PropertyDrawer 
 {
     public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
     {
         SoundSelector soundSelectorAttribute = attribute as SoundSelector;
 
         Rect labelPos = new Rect (position.x, position.y, position.width * 0.4f, position.height);
         Rect popupPos = new Rect (position.x + position.width * 0.4f, position.y, position.width * 0.6f, position.height);
 
         var index = soundSelectorAttribute.names.FindIndex(s => s == property.stringValue);
 
         EditorGUI.LabelField(labelPos, property.displayName);
 
         index = EditorGUI.Popup(popupPos, index, soundSelectorAttribute.keys.ToArray());
 
         if (index >= 0) {
             property.stringValue = soundSelectorAttribute.names[index];
         }
         else {
             //default value
             property.stringValue = soundSelectorAttribute.names[0];
         }
     }
 }

does anyone know what the cause of this could be?

Much appreciated!