generate noise when using Ulysses Attention

### Describe the bug

When running **Wan2.1-T2V-14B-Diffusers** model with **Ulysses Attention**, the last few frames of the generated vedio are completely noisy.

### Reproduction

```
# infer_wan_t2v.py

import numpy as np

import torch

from diffusers import AutoencoderKLWan, WanPipeline, ContextParallelConfig, WanTransformer3DModel
from diffusers.utils import export_to_video
from diffusers.hooks import apply_group_offloading

import os

def launched_with_torchrun() -> bool:
return (
"RANK" in os.environ
and "WORLD_SIZE" in os.environ
and "LOCAL_RANK" in os.environ
)

cpu_offload = True
vae_tiling = True

model_id = "/home/weights/Wan2.1-T2V-14B-Diffusers/"
height = 480
width = 832
prompt = "A cat walks on the grass, realistic"
negative_prompt = "Bright tones, overexposed, static, blurred details, subtitles, style, works, paintings, images, static, overall gray, worst quality, low quality, JPEG compression residue, ugly, incomplete, extra fingers, poorly drawn hands, poorly drawn faces, deformed, disfigured, misshapen limbs, fused fingers, still picture, messy background, three legs, many people in the background, walking backwards"

try:
if launched_with_torchrun():
torch.distributed.init_process_group("nccl")
rank = torch.distributed.get_rank()
device = torch.device("cuda", rank % torch.cuda.device_count())
world_size = torch.distributed.get_world_size()
else:
rank = 0
device = torch.device("cuda")
torch.cuda.set_device(device)

onload_device = device
offload_device = torch.device("cpu")

vae = AutoencoderKLWan.from_pretrained(model_id, subfolder="vae", torch_dtype=torch.float32)
pipe = WanPipeline.from_pretrained(model_id, vae=vae, torch_dtype=torch.bfloat16)

pipe.transformer.set_attention_backend("_native_cudnn")

if launched_with_torchrun():
pipe.transformer.enable_parallelism(config=ContextParallelConfig(ulysses_degree=world_size))

if cpu_offload:
apply_group_offloading(
pipe.text_encoder,
onload_device=onload_device,
offload_device=offload_device,
offload_type="leaf_level",
use_stream=True,
)
pipe.transformer.enable_group_offload(
onload_device=onload_device,
offload_device=offload_device,
offload_type="leaf_level",
use_stream=True
)
pipe.vae.enable_group_offload(
onload_device=onload_device,
offload_device=offload_device,
offload_type="leaf_level",
use_stream=True
)
else:
pipe.to(device)

if vae_tiling:
pipe.vae.enable_tiling(
tile_sample_min_height=int(height / 2 * 3),
tile_sample_min_width=int(width / 2 * 3),
tile_sample_stride_height=int((height + 1) / 2),
tile_sample_stride_width=int((width + 1) / 2),
)

output = pipe(
prompt=prompt, negative_prompt=negative_prompt, height=height, width=width, num_frames=49, guidance_scale=5.0, num_inference_steps=3
).frames[0]

if rank == 0:
export_to_video(output, "output.mp4", fps=16)

except Exception as e:
print(f"An error occurred: {e}")
raise e

finally:
if launched_with_torchrun():
if torch.distributed.is_initialized():
torch.distributed.destroy_process_group()
```

run with command
```
torchrun --nproc_per_node=8 infer_wan_t2v.py
```

### Logs

https://github.com/user-attachments/assets/326d3745-f377-4403-aa5b-8d59462adf46

### System Info

diffusers: 0.36.0.dev0
compile the main-branch locally

### Who can help?

_No response_

Start with the provided infer_wan_t2v.py reproduction and run it with torchrun --nproc_per_node=8 using WanPipeline and ContextParallelConfig with Ulysses attention. Inspect the Wan transformer parallelism path and compare the generated 49-frame output, focusing on the noisy final frames. Done means the reproduced multi-process generation no longer produces corrupted final frames.

Scritto dal modello di indicizzazione a partire dal testo della issue.