This is an interesting bug...
1. Create a subsystem
2. Add a module in the subsystem with an inspector... for example, Scaler - call this subsys1.Scaler
3. Copy and paste the subsystem. Now you have subsys2.Scaler
4. Now, open the inspector of subsys1.Scaler
5. Without closing the inspector, open the inspector for subsys2.Scaler... what you'll see is that the other inspector will close first and then the new inspector will be opened. Both of them cannot be opened simultaneously.
Copying and pasting the scaler within the same subsystem works fine. It's only when you copy and paste the subsystem itself.