• [ X] I have marked all applicable categories:
  • exception-raising bug
  • visual output bug
• [X ] I have visited the source website, and in particular
  read the known issues
• I have searched through the issue tracker for duplicates
• I have mentioned version numbers, operating system and
  environment, where applicable:

  import tqdm, sys
  print(tqdm.__version__, sys.version, sys.platform)

4.63.0 3.8.10 (default, Jun 2 2021, 10:49:15)
[GCC 9.4.0] linux

from tqdm import tqdm
import time
from concurrent.futures import ThreadPoolExecutor, as_completed

layers = [{"size" : 1000}, {"size" : 1000}]

The following code, randomly produces a 3rd line duplicating the content of the previous line:

def download_layer(layer, position):
    total = layer['size']
    with tqdm(total=total, position=position, ascii=True) as pbar:
        for n in range(int(total / 50)):
            time.sleep(0.01)
            pbar.update(50)


with ThreadPoolExecutor(max_workers=len(layers)) as ex:
    futures = []
    for i, layer in enumerate(layers):
        futures.append(ex.submit(download_layer, layer, i))
    for future in as_completed(futures):
        result = future.result()
```

It was tested running python from Windows + WSL2 and the VSCode Terminal.