How to keep track of faulted items in TPL pipeline in (thread)safe way

Question

I am using TPL pipeline design together with Stephen Cleary's Try library In short it wraps value/exception and floats it down the pipeline. So even items that have thrown exceptions inside their processing methods, at the end when I await resultsBlock.Completion; have Status=RunToCompletion. So I need other way how to register faulted items. Here is small sample:

var downloadBlock = new TransformBlock<int, Try<int>>(construct => Try.Create(() =>
{
    //SomeProcessingMethod();
    return 1;
}));
var processBlock = new TransformBlock<Try<int>, Try<int>>(construct => construct.Map(value =>
{
    //SomeProcessingMethod();
    return 1;
}));
var resultsBlock = new ActionBlock<Try<int>>(construct =>
{
    if (construct.IsException)
    {
        var exception = construct.Exception;
        switch (exception)
        {
            case GoogleApiException gex:
                //_notificationService.NotifyUser("OMG, my dear sir, I think I messed something up:/"
                //Register that this item was faulted, so we know that we need to retry it.
                break;
            default:
                break;
        }
    }
});

One solution would be to create a List<int> FaultedItems; where I would insert all faulted items in my Exception handling block and then after await resultsBlock.Completion; I could check if the list is not empty and create new pipeline for faulted items. My question is if I use a List<int> am I at risk of running into problems with thread safety if I decide to play with MaxDegreeOfParallelism settings and I'd be better off using some ConcurrentCollection? Or maybe this approach is flawed in some other way?