When you undo a RemoveItemCmd and its Item member is an Arrow, you don't get an ArrowCreated event. In user terms, if you have two boxes connected by an arrow, delete the arrow, and the click undo, there is no ArrowCreated event fired in code. (Note that the inverse does work, however. You can create an arrow between two boxes, click undo, and get an ArrowDeleted event.)

Also, if you delete a box with arrows connected and undo that, you don't get ArrowCreated events for any of the arrows.

Note that in both cases, you do get ArrowDeleted events (one for each attached arrow in the box case).

I've done a temporary workaround to fake the firing of the events when I detect these scenarios in code.