To reproduce :

1.Download and Open attached project
2.Open "StartScene" scene
3.Press Play

Reproduced on: 5.5.0p26 , 5.6.0b2, 5.4.3p3, 5.3.7p2, 5.2.5f1

Expected result : "StartScene" changes to "TestScene".
Actual result: Scene is not changing.

Workaround: Go to "TestScene", select Cylinder object and remove material reference from Test Scene Script(Make it to be none).

Note: First time the game is played scene loads as expected, all the other times scene is not loaded. With other materials reference attached to the Test Scene Script(For example : deffault-diffuse) scene loads as expected. Problem appears with the user imported(new_graph) material.