Level Streaming Transition Problem

hi…i have some questions about level streaming. I have two levels
level A is a level that plays a few video clips. When video finishes, it loads level B.
level B is filled with meshes. BeginPlay starts with playing a sequence using the sequencer.
Instead of using Open Level node, I add existing level B to level A, and use “load streaming level” blueprint node to load level B. It reduces the transition time between two levels.
However, my player spawns in the middle of the air during the transition before the level is loaded.
How could I fix this? Checking “Block on load” does not work.

I also tried to use an empty pawn but the level is still seen for half a second before it is fully loaded.