Hello, I've checked the level :) There shouldn't be any problem somehow.
• Have you tried pressing Jump + Directional (left or right) button at the same time?
• Try jumping off the ladder just before you reach the top of it.
• What operating system are you currently using? Does the error still persist after reloading the game?
I tried on different browsers it seems working fine, but let me know if the problem is still there so I could check the certain area of the level thoroughly. Thank you!