Problem is that a judge has limited investigative powers. Which makes sense since judges aren't in the investigation business. A summons is the tool a judge uses to force someone to come to court. Can only issue a summons for an opn hearing. This is the result. It would probably be best if the judge had referred the matter to the prosecutor for investigation, or appointed a special prosecutor for that purpose.
To be honest, this is the purpose of the public defender's office having investigators on staff, to investigate claims of this nature so that the PD can file appropriate motions to get the case back into court. If the judge finds new evidence requiring the case to be re-opened, the judge has now become a witness, necessitating that the matter be turned over to a second judge to preside over, mucking up two courts in the process. Should have referred it out, and avoided all of the headaches. At least then, it would likely be a special grand jury, and thus protected.