void closeDBFfile();

When you finish working with a DBF file you have to close it.

{
    cdbfapiPlus* dbf = new cdbfapiPlus();
    if (!dbf) return;
    
    if (dbf->openDBFfile("c:\\tmp\\example.dbf"))
    {
        // your code
        dbf->closeDBFFile();
    }
    delete(dbf);
}