In defining bbox, there are cases where the data type is converted to float64 format.
If possible, it is recommended to load with numpy when loading data, and to batch convert to torch format right before training the model.
boxes = df[['xmin','ymin','xmax','ymax']].values

to
np.array(df[['xmin','ymin','xmax','ymax']].values, dtype = np.float32)

Whether or not Augmentation is applied will probably work.