Yes, I completed the game. I think I got 81 of the cubes and I finished the game in about ~3 hours. If I’m not mistaken I think I got a B.
I just played through that same stage again (last level “T”, second stage) and the exact same bug reoccurred.
Ah cool. Thank you so much for double-checking. I'll try and take a look at a fix today. :D
Nice! Great work. You can go back and redo older worlds to bring your time down if you want to boost your rank and get the other ending artwork.