To reproduce:
1. Open attached project
2. Open "canvas_scaler" scene
3. Open Game window
4. Click pause and then Play
5. Notice that game object appeared in the corner
6. Play the scene without pause button
7. Notice where game object is now

Actual behavior: CanvasScaler in first frame does not update scale (results shown in step 5)
Expected behavior: view in 5 and 7 steps should be the same

Workaround: add
scaler.enabled = false;
scaler.enabled = true;
to update scale on first frame