Mappers 21/23/25 are a mess (especially the VRC4 variants).
Boku Dracula-kun was one of my original VRC4e test carts so it should work.
I'll have to recheck the Mapper 21 code for the handling of Wai Wai World 2. I used Ganbare Goemon Gaiden 2 as my Mapper 21 test cart but it uses a different VRC4 variant.
I'm away from all of my cart reader stuff at the moment. I'll retest the mappers when I'm able to.