Checking check box in graph doesn't fire its state changed event

I’ve seen this question asked but not answered, sadly - and I have pretty much the same problem. In my case, I have two check boxes, if one is checked, the other one gets unchecked.

Changing check box state in the graph changes just the checkbox visually, but doesn’t start the OnCheckStateChanged event the check box is binded to. How to actually start the event of the check box changed from the graph?