Cannot get the benchmark result using KPConv on S3DIS dataset.

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D-ML/issues).
- [X] I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

Using RandLA-Net on S3DIS with the default randlanet_s3dis.yml can get the benchmark result.
But I cannot get the ideal mIoU result when using KPConv with the default config file on the same S3DIS dataset. The mIoU fluctuated at 10%.

This is my code for training.

from ml3d.torch.models import kpconv

from ml3d.torch.pipelines import semantic_segmentation

from ml3d.datasets.s3dis import *

import torch

import open3d.ml as _ml3d

import sys, os

if __name__ == '__main__':
os.chdir(sys.path[0])

cfg_file = "./ml3d/configs/kpconv_s3dis.yml"
cfg = _ml3d.utils.Config.load_from_file(cfg_file)

dataset = S3DIS(**cfg.dataset)

model=kpconv.KPFCNN(**cfg.model)

pipeline = semantic_segmentation.SemanticSegmentation(model=model, dataset=dataset,**cfg.pipeline)

pipeline.run_train()

Can anyone get the reported result? I would appreciate it if you can give me some suggestions.

Cheers,

Eric.