Index: lams_central/web/includes/javascript/authoring/authoringProperty.js
===================================================================
diff -u -reff4591166587e12af17581dc551a6104673cceb -r82268377d31a6b2c88a736ffdf368156d92af866
--- lams_central/web/includes/javascript/authoring/authoringProperty.js	(.../authoringProperty.js)	(revision eff4591166587e12af17581dc551a6104673cceb)
+++ lams_central/web/includes/javascript/authoring/authoringProperty.js	(.../authoringProperty.js)	(revision 82268377d31a6b2c88a736ffdf368156d92af866)
@@ -1806,6 +1806,7 @@
 				// if user dragged the dialog at least once, it does not automatically change its position anymore
 				return;
 			}
+			
 			var box = object.items.getBBox(),
 				canvasOffset = canvas.offset(),
 				canvasWidth = canvas.width(),
@@ -1829,9 +1830,12 @@
 				};
 			}		
 			
+			x -= canvas.scrollLeft();
+			y -= canvas.scrollTop();
+			
 			dialog.offset({
-				'left' : x,
-				'top'  : y
+				'left' : Math.max(canvasOffset.left, Math.round(x)),
+				'top'  : Math.max(canvasOffset.top,  Math.round(y))
 			});
 		});