Repro Steps:

1) Grab Z3L_LiveDemo from the InternalSamples GitHub.
2) Within the Navigator, navigate to the layer named 'InterfaceGrid'. Click on it to make the Grid's Rows and Columns visible on the stage.
3) Grab the adorner sitting between Column 2 and Column 3 (where Col 0 is the left margin, Col 1 is to the left of the mech, and Col2 is in the centre of the screen)
4) Drag the adorner far rightwards off of the stage, and drag it far leftwards back onto the stage, and past the left edge of the stage.

Observe the viewport disapearing from view.
Observe in certain instances, the application crashing.

Expected Results:
The viewport continues to render properly regardless of the position of a Grid Column