In addition to any hearing required under this subsection or § 5-306(b)(2) of this subtitle, a juvenile court may hold a hearing before entering a guardianship order under § 5-320(a)(1) of this subtitle or otherwise ruling on a guardianship petition. If a party becomes aware, before a juvenile court rules on a guardianship petition, that a condition of consent under § 5-320(b) of this subtitle may not be fulfilled: the party promptly shall: file notice with the juvenile court; give notice to all of the other parties; and if consent was received from a governmental unit or person who is not a party, give notice to that unit or person; the juvenile court shall schedule a hearing to occur within 30 days after the filing of the notice; and if the party, unit, or person whose condition cannot be fulfilled fails to enter into a new consent, the juvenile court shall set the case in for a prompt trial on the merits of the petition. Before a juvenile court grants guardianship under § 5-320(a)(2) of this subtitle, the juvenile court shall hold a trial on the merits of the petition. Before a trial or other hearing under this section, a juvenile court shall give notice to all of the parties.