Any party in interest may, within twenty days after notice of a workers' compensation judge's adjudication shall have been served upon him, take an appeal to the board on the ground: (1) that the adjudication is not in conformity with the terms of this act, or that the workers' compensation judge committed any other error of law; (2) that the findings of fact and adjudication was unwarranted by sufficient, competent evidence or was procured by fraud, coercion, or other improper conduct of any party in interest. The board may, upon cause shown, extend the time provided in this article¹ for taking such appeal or for the filing of an answer or other pleading.