Система прекращает импорт

I have a system that looks in a client informed folder for OpenFileDialog for all XML, then reads them, and then imports the data into a SQL Server database.
The problem is that after a while, it stops importing, and the system hangs, but in monitoring everything is still running. If I import one by one, I can import them all, but the system must be importing hundreds of XML at a time.
Another problem is a method that returns true or false when XML has already been imported, if I start debugging, the method returns false, if I let it run without delegation, it returns true.

    //Counts how many files there are in the path of the first XML folder
    int cte = 0;
    if (Directory.Exists(caminhocte))
    {
        foreach (string filePath in Directory.EnumerateFiles(caminhocte, "*.xml", SearchOption.AllDirectories))
        {
            cte++;
        }
    }
    //Counts how many files there are in the path of the second XML folder
    int nfe = 0;
    if (Directory.Exists(caminhonfe))
    {
        foreach (string filePath in Directory.EnumerateFiles(caminhonfe, "*.xml", SearchOption.AllDirectories))
        {
            nfe++;
        }
    }

    //Displays a message with how much XML will be imported, and asks if he wants to continue with the import
    MessageBoxButtons buttonn = MessageBoxButtons.YesNo;
    MessageBoxIcon iconn = MessageBoxIcon.Information;
    string messagen = string.Format("{0}{1}{2}{3}{4}{5}{6}{7}{8}",
        "Detalhes: ", Environment.NewLine,
        "Numero de XML na pasta CTE: ", cte, Environment.NewLine,
        "Numero de XML na pasta NFE: ", nfe, Environment.NewLine,
        "Deseja continuar com a importação?");
    string titlen = "Aviso";
    DialogResult result = MessageBox.Show(messagen, titlen, buttonn, iconn);
    //If you do not want to continue importing, the system returns
    if (result == DialogResult.No)
    {
        return;
    }


    int ctes = 0;
    int ctee = 0;
    if (Directory.Exists(caminhocte))
    {
        ImportaXML(caminhocte, "CTE");
        ctes = xmlimportsucess;
        ctee = xmlimporterror;
    }
    int nfes = 0;
    int nfee = 0;
    if (Directory.Exists(caminhonfe))
    {
        ImportaXML(caminhonfe, "NFE");
        nfes = xmlimportsucess;
        nfee = xmlimporterror;
    }
    xmlimporterror = 0;
    xmlimportsucess = 0;

    //Build a message that will be generated at the end of the process in txt form.
    string messagesucess = string.Format("{0}{1}{2}{3}{4}{5}{6}{7}{8}{9}{10}{11}{12}{13}{14}{15}{16}",
        "Informações da importação do CTE", Environment.NewLine,
        "CTE importado com sucesso: ", ctes, Environment.NewLine,
        "CTE não importado(Erro): ", ctee, Environment.NewLine,
        "Informações da importação da NFe", Environment.NewLine,
        "NFe importada com sucesso: ", nfes, Environment.NewLine,
        "NFe não importado(Erro): ", nfee, Environment.NewLine,
        "-----------------------------------"
        );

    MessageBoxButtons buttonF = MessageBoxButtons.OK;
    MessageBoxIcon iconF = MessageBoxIcon.Information;
    string messageF = "Arquivo de Registro do log foi gerado com sucesso.";
    string titleF = "Aviso";
    MessageBox.Show(messageF, titleF, buttonF, iconF);

    //Create folder and log txt file
    registrarLog(messagesucess, "", "Reg");
    GC.Collect();




//This method will get the path and type case, in the DirectXML class it will read the XML and see if it is a CTE or NFE and will import the XML information.
//If it gives an error, it will log a log.
void ImportaXML(string caminho, string tipo)
{
    xmlimportsucess = 0;
    xmlimporterror = 0;
    foreach (string filePath in Directory.EnumerateFiles(caminho, "*.xml", SearchOption.AllDirectories))
    {
        try
        {
            DirecionarXML dir = new DirecionarXML();
            dir.direcionarXML(filePath, "", tipo);
            xmlimportsucess++;
        }
        catch (Exception ex)
        {
            registrarLog(ex.Message, filePath, "Err");
            xmlimporterror++;
        }
    }
}