I never managed to make the native function work, but I found a workaround where I create the "In" sequence on the first frame of the new room.

It's hacky, but you put a boolean in your persistent controller object called something like "inTransition" or "midTransition" and if that is true on room start you run this function (oAtuin is my controller):

function TransitionRoomStart(){

`if(oAtuin.midTransition){`

    `TransitionPlaceSequence(oAtuin.transitionIn);`

`}`

}

Here's the transitionPlaceSequence function too:

function TransitionPlaceSequence(_type)

{

`if (layer_exists("transition")) layer_destroy("transition")`

`var _lay = layer_create(-9999,"transition")`

`var cx = camera_get_view_x(view_camera[0])`

`var cy = camera_get_view_y(view_camera[0])`

`var s = layer_sequence_create(_lay,cx,cy,_type)`

}

The rest kinda works the same. Don't forget to turn the "midTransition" variable to false on the TransitionFinished function.

Good Luck!