Section 16. When in any case before the department it appears that compensation has been paid or when in any such case there appears of record a finding that the employee is entitled to compensation, no subsequent finding by a member or the reviewing board discontinuing compensation on the ground that the employee’s incapacity has ceased shall be considered final as a matter of fact or res adjudicata as a matter of law, and such employee or his dependents, in the event of his death, may have further hearings as to whether his incapacity or death is or was the result of the injury for which he received compensation; provided, however, that if the board shall determine that the petition for such rehearing is without merit or frivolous, the employee or his dependents shall not thereafter be entitled to file any subsequent petition thereof except for cause shown and in the discretion of the member to whom such subsequent petition may be referred; and, provided further, that, in the event of the death of the employee, such a petition for a rehearing shall be filed within three months from the time of his decease and within one year from the date of the finding terminating his compensation.