Mmmm I'm unable to replicate the bug. What emulator are you using? Also did you respawn from the checkpoint before encounting the bug? thanks
I'm using the suggested emulator (snes9x 1.63), The level itself was broken to have me not go below the top half of the level, and I was able to run on the top half of it to get to a starman block with some special coins to get me out of the original problem but, once I made it to the checkpoint before the quicksand section, I died, sent me to a new checkpoint I haven't been too yet, then I made it to the spot shown in the screenshot by using the cape feather to get the key to the exit pipe.