EF Core and Async Retention

Question

I am testing bulk import using EF Core and trying to save asynchronously.

I am trying to add 100 objects at a time and then asynchronously save and repeat until they are saved. Sometimes I get a PK error because it is trying to add two objects with the same identifier to the database. None of the added objects has an identifier; identifiers are sequences that are automatically generated.

The code:

public async Task<bool> BulkAddAsync(IEnumerable<VehicleCatalogModel> models)
{
    _dbContext.ChangeTracker.AutoDetectChangesEnabled = false;
    try
    {
        var entities = models.Select(ToEntity);
        _dbContext.Set<VehicleCatalog>().AddRange(entities);
        await _dbContext.SaveChangesAsync();
    }
    catch (Exception ex)
    {
        _logger.LogError(0, ex, "An Error occurred during the import");
        return false;
    }
    return true;
}

I call the method in the xunit test, which generates a list of test data and calls the import

var result = manager.BulkAddAsync(modelsToAdd.AsEnumerable());
var counter = 0;
while (!result.IsCompleted && counter < 10)
{
    Thread.Sleep(6000);
    counter++;
}
Assert.True(result.IsCompleted && result.Result);

100 , , , . - , , ? ?