Hi ace,
I assume that you are using the latest version of syncfusion assemblies.
I am afraid but I am not able to reproduce the issue.
I set the same code snippet to disable height modification.
The Node does not allow height to be changed then after.
The sample file is attached herewith for your perusal.
Also, by default the diagram convention of "NodeClick" event is to cycle through the ZOrders of every node present at a same point of mouse click, starting from the top most node to the node lowest at the "clicked mouse point".
Let me know if this helps.
Happy coding!
- Ajeet
Diagram_WF_NodeEvents_86a47cd6.zip