My lambda function is unable to unzip a file

I deployed a flask app to lambda that includes a function that unzip a small file (124ko), but nothing works as expected. The unzipping clearly fail and I can't find the reason.

2021-03-23T12:12:46.346+01:00	error [/tmp/39423ff39f7f4378a8f835a20fdcb688.zip]: missing 3183398882 bytes in zipfile

2021-03-23T12:12:46.346+01:00	(attempting to process anyway)

2021-03-23T12:12:46.346+01:00	error [/tmp/39423ff39f7f4378a8f835a20fdcb688.zip]: start of central directory not found;


2021-03-23T12:12:46.346+01:00	zipfile corrupt.

2021-03-23T12:12:46.346+01:00	(please check that you have transferred or created the zipfile in the

2021-03-23T12:12:46.346+01:00	appropriate BINARY mode and that you have compiled UnZip properly)

There is no problem when testing locally and the zip file is okay. So I guess the issue comes from lambda.

The code :

with open(file_path, "wb") as binary_file:
        binary_file.write(file_content)

Expected behavior : The file should unzip without problem just as it does when the app runs locally or in heroku.

P.S. I am using postman for testing

EDIT : also tried to extract with zipfile

with zipfile.ZipFile('/tmp/myfile.zip', 'r') as z:
    z.extractall(fil_dir)

and got the following error :

raise BadZipFile("Bad magic number for central directory")

Originally I was extracting with

os.system("unzip -qq %s -d %s" % (file_path,file_dir))

Any suggestion ?

Start with the Lambda function that writes file_content to /tmp/file_path and compare the bytes received through Postman with the local or Heroku input. Verify the saved archive with the shown zipfile.ZipFile call before extraction; done means the same archive opens and extracts successfully in Lambda.