Attached is the program a student has used to create a platformer. When the dog reaches the portal and touches it, as opposed to going to the next stage, the screen turns black. No other student has this difficulty and I haven't been able to see anything incorrect in the code.
if you look in the stage, he makes the stage hide when it receives stage 2 and stage 3. hiding the stage makes the stage turn black. If you remove the hide blocks, it'll work fine (although it can never go to stage 3 because when the dog is touching the portal, it will always go to stage 2)