The Battle of Stone-in-the-Wood was filmed in late July 2018. One day, after all the main puppets had already been gathered on the set, Stage B caught fire. Fire crews from Langly, Slough and Windsor arrived on the scene and director Louis Leterrier put himself in danger to save the main puppet characters, which in the end suffered not so much from the fire but more so from the sprinklers. The animatronic heads of Aughra and the Hunter were severely damaged, but the production managed to repair everything they needed in three days in order to resume filming.
As skekTek says the line, "I will need to find a much stronger source of connective tissue to augment the fibroblasts", his voice starts to sound the way it does in the film.