The decisions and award in the case shall conform to the findings and conclusions in such report insofar as it is restricted to medical questions, except that either party may, within ten days after receipt of a copy of the report, file written objection thereto with the commission; provided, the report shall not be binding on the commission if it be proven that the conclusion of the board upon a medical question be erroneous, due to fraud, undue influence, or mistake of law or material fact.