G4IonTable: FindIon with excitation level, nullptrs

Dear experts,
I am developing some code for the DD4hep software, I am using Geant4 version 10.7 and I am generating MC events with Pythia8.3 Angantyr model.
I am trying to access particle definition objects of excited ions from the pdgID in this way,

    int id = particle->pdgID;  // is 10 L ZZZ AAA I
    int L, A, Z, lvl;
    id -= 1000000000; 
    L = id / 10000000; id %= 10000000;
    Z = id / 10000;    id %= 10000;
    A = id / 10;       id %= 10;
    lvl = id;
    G4double E = 0.0;
    G4IonTable*      tab_ion = G4IonTable::GetIonTable();
    G4ParticleDefinition* def_ion = tab_ion->FindIon(Z, A, lvl);

The FindIon method returns a null pointer for some of these states. For example, for pdg ID equal to 1000691759 and 1000711809. What is the reason for this?
Does this state have a defined excitation energy?
What does it mean the warning message: “Isomer level 9 may be ambiguous”?

I would like to specify that not all the ions with isomer level equal to 9 are null pointers.
Here an example of some printouts to get pdgID, pointer and excitation energy (using the method ((const G4Ions*)(def_ion))->GetExcitationEnergy();).
It works for this case:

Creating ion 1000230499
Found ion 0x15fd1140
GetIsomerLevel, 9, excitation energy E=0.152928

But not for this one:

Creating ion 1000711809
Found Ion ? 0

Thanks for your support.