As all the animals were walking back at the end of the game, the game crashed and I got a dialogue box pop up which said:

Adventure Game Studio
An error has occurred. Please contact the game author for support, as this is likely to be a scripting error and not a bug in AGS (ACI version 3.4.0.12)
in "room4.asc", line 52
Error: MoveCharacter: character not in current room

Edit: replayed the game and there was no issue this time.