As an update I’ve been able to get a test case of num_workers > 0 to work after setting the environment variable OMP_NUM_THREADS=2 though I’m not sure this had anything to do with it.  Because when I then attempt to enumerate over the loader in the actual training loop the same error occurs.  So something about being nested in the training loop is causing the thread confusion.  I’d love to find a solution to this.
But just for information for others stumbling on this thread.  Just the act of correcting my dataset creation and then drawing from it with the default DataLoader is much faster than trying to build the dataset within the dataloader and skipping the Custom DataSet as I was previously attempting.