Lake Cave, Magical Melody Options

[Jack_White]

I recently started a new data on MM and it's currently the end of the winter. I have 3 days until Spring. I really want to reach the bottom of the Lake Cave. I always reach 91 and then I start going back up. It's getting really annoying! I keep on going from 91 back to somewhere in the 80's, then somewhere in the 70's and then I keep on going back to 91 and it repeats. I don't get it. On level 80 and level 91, is it always this hard? I always get the question marks and go up. On my first data, this cave was a breeze. This time, it's extremely hard. Is there any strategy or tip to get to the bottom of this never ending jinx? Or is it just pure luck? Thanks for your help.