Hey @len zm, as Jason suggested, reverting back to an earlier version of your model is the best course of action in this case. You can sometimes achieve temporary control of your model again if you go into the Tree and delete the ConveyorSystem. Then you can see your model again, but errors may still be present. Ben points out in a post he made a while back some key ways to mitigate file corruption when it happens. I suggest saving iterations of your file with Auto Increment Save (or Ctrl + Shift + S). That way you have different iterations of your model you can revert back to if you run into this problem in the future.

Furthermore, avoid using Ctrl + Z or undo when working with Conveyors. There are some bugs the devs are aware of when dealing with undoing changes on Conveyors.