3D symbols (default from pallette or custom) created in a model can only be show in one drawing view at a time (similar to dimensions). This can cause problems if the symbol contains important information. One example might be if a drawing shows a front view and a iso view where the symbol should be seen in both views.
The current workaround being used is to create multiple instances of the same 3D symbol (one for each veiw in the drawing where it needs to show up) on top of each other in trhe model. Weak...but it works OK.