Hi @mrosen!
I used this great post on overlap to help focus on finding the issue. I looked where the sprite might be assigned to something that makes the program think it is no longer a sprite. On line 87, ball_sprite is assigned to 280 BUT I think the intent was to assign ball_sprite**.y** to 280. When I did that, I no longer got the error. Let us know if that helped things on your end.
~Michelle