Reproduction Steps:
1. Open User's project
2. Set "Canvas" Sort Order = 2 and "Panel" Sort Order = 0
3. Notice that the Text is OVER the Panel
4. Run the scene
5. Notice that the Text is UNDER the Panel
6. Increase "Canvas" to 3 and "Panel" to 1
7. Notice that it switched again
-Note: There is picture "canvas_.png" attached by User showing the examples.

Expected behaviour: Consistent sorting order, which does not differ depending on the last change or if the project is running or not.
Actual: It does differ. The scene view before run and while it is running can be very different.

Reproduced in versions: Unity 5.2.4f1, 5.3.5p1, 5.3.5p2, 5.4.0b16, 5.4.0b20