Reproduction steps:
1. Open the attached project (UI_case_857956.zip);
2. Enter in the Play mode;
3. Return to Scene window;
4. Select UI\Inventory(UI) and enable a component Canvas;

Actual result: The new created gameobjects are display in the center of canvas.
Expected result: The new created gameobjects should be displayed like their parent position.

Workaround: If you change UI\Inventory(UI) Rect Transform position, the new objects goes to their parent position. Also, if you enable the canvas, before creating the new objects, they are displayed in the correct place.

Reproduced with: 5.5.0f1, 5.5.0f3, 5.6.0a6
Not reproducible: 5.3.6p4, 5.4.1f1, 5.4.3f1