Here are two bugs related to gizmos. Sorry, can’t really create playground examples since these are related to hosting the engine/canvas in an app specific way.
Gizmos do not work well if canvas is inside a “zoomed” DIV.
This one is really strange. Gizmos are placed incorrectly when two engines with two canvases placed next too each other. In the latter part of the video, see how clicking in the left canvas shows the gizmo in the right canvas.
The test app is here: Bjorn's Playbooks