so you don't need to go into the actual mineshaft, you just need access to the top entrance, then follow my previous instructions and you'll find the scene, hope this helps 👍🏻
I tried going to the left but I'm confused by "there will be a slight indent in the cliff on the right side, land on it and reveal a secret room". I'm going left but there is no "indent" anywhere where I can fall. The only boxes I find by going left are two boxes next to a wall.