Geant4 c++ segmentation fault

Question

My code is based on the Geant4 c++ physics toolkit but I believe my problem may be more related to basic programming knowledge. Essentially a particle moves through the simulation in a loop of steps, and I am trying to get the x-position where it leaves a particular volume and enters another. To do this, I have added the last 'if' block to the "SteppingAction.cc" source file which, upon the particle crossing the relevant boundary, gets the 3-D track position, prints the x value, and then writes the x value as a double to a csv file. This successfully prints the correct position but after the simulation finishes iterating the rest of the particles and before the event is visualized, I get a segmentation fault and crash. This happens even if I delete either the print line or the csv write line, but if I remove both leaving only the line which gets the track position, I no longer receive the fault.

G4AnalysisManager* analysisManager = G4AnalysisManager::Instance();

LXeSteppingAction::LXeSteppingAction(LXeEventAction* ea)
    : fOneStepPrimaries(false)
    , fEventAction(ea)
{
    fSteppingMessenger = new LXeSteppingMessenger(this);
    fExpectedNextStatus = Undefined;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

LXeSteppingAction::~LXeSteppingAction() { delete fSteppingMessenger; }

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

void LXeSteppingAction::UserSteppingAction(const G4Step* theStep)
{
    G4Track* theTrack = theStep->GetTrack();
    const G4ParticleDefinition* part = theTrack->GetDefinition();
    G4int pdg = part->GetPDGEncoding();

    if (theTrack->GetCurrentStepNumber() == 1)
        fExpectedNextStatus = Undefined;

    LXeUserTrackInformation* trackInformation =
        static_cast<LXeUserTrackInformation*>(theTrack->GetUserInformation());

    G4StepPoint* thePrePoint = theStep->GetPreStepPoint();
    G4VPhysicalVolume* thePrePV = thePrePoint->GetPhysicalVolume();

    G4StepPoint* thePostPoint = theStep->GetPostStepPoint();
    G4VPhysicalVolume* thePostPV = thePostPoint->GetPhysicalVolume();

    G4OpBoundaryProcessStatus boundaryStatus = Undefined;

    if (theTrack->GetParentID() == 0)
    {
        if (thePostPV->GetName() == "scintillator1")
        {
            if (thePrePV->GetName() != "scintillator1")
            {
                CLHEP::Hep3Vector Det1 = theTrack->GetPosition();
                std::cout << Det1[0] << std::endl;
                analysisManager->FillNtupleDColumn(0, 14, Det1[0]);
            }
        }
    }
}

I have also tried writing a separate function to write to the csv file, and calling from within the if statement, with the same result. I think I may be overlooking something basic, any ideas? Thank you.