Thanks for playing and detailed feedback. Jumping on the boxes is the main mechanic of the game, glad you figured it out on your own. I tried to explain it through level design and let the player figure it out without explaining using text (Not sure if I did a good job on that).
And yes, the boxes falling after a few seconds is intended. I did plan to put some visuals or at least a sound but forgot :D
The not-so-accurate box placement after dropping is a bug. I will try to add air strafing thanks for that suggestion.