If you are using multiple workers (via num_workers >= 1) you shouldn’t change attributes of the Dataset stored in the DataLoader, as this would most liktly only manipulate the copy of the Dataset and won’t be reflected on the original Dataset.
In your code snippet you are using self._training_loader.dataset.resample_scale() inside the self._training_loader loop, which would be the case.
If you need to manipulate the underlying dataset, you could try to apply the changes before starting the next epoch.