Bug Report - Bird dying not undoing move

[SuperMuffinBros]

I'm playing on the Epic Games Snakebird Complete edition.
On level Star3 of the original Snakebird, and if the first move you make is an upward move with the green bird, the blue bird falls into the spikes, but you can continue playing with the other birds as if the blue bird wasn't dead...
This only happens if the move in question was done before any other.

Don't know why.