Uploading large files using chunks

Hello: I am using this Python code to upload a large zip file (2-4 GB). I am trying to upload the file in chunks, however I am getting a "dropbox.exceptions.ApiError('some_random_numbers', UploadSessionLookupError(u'incorrect_offset', UploadSessionOffsetError(correct_offset=540)))

Here is my code that is uploading the zip file using chunks (from StackOverflow)

f = open(outputName)
file_size = os.path.getsize(outputName)

CHUNK_SIZE = 10000

if file_size <= CHUNK_SIZE:

	print dbx.files_upload(f.read(), backupPath)

else:

	upload_session_start_result = dbx.files_upload_session_start(f.read(CHUNK_SIZE))
	cursor = dropbox.files.UploadSessionCursor(session_id=upload_session_start_result.session_id,
												   offset=f.tell())
	commit = dropbox.files.CommitInfo(path=backupPath)

	while f.tell() < file_size:
		if ((file_size - f.tell()) <= CHUNK_SIZE):
			print dbx.files_upload_session_finish(f.read(CHUNK_SIZE),
									cursor,
									commit)
		else:
			dbx.files_upload_session_append(f.read(CHUNK_SIZE),cursor.session_id,cursor.offset)
			#dbx.files_upload_session_append_v2(f.read(CHUNK_SIZE), cursor)
			cursor.offset = f.tell()

 I tried v2 for files_upload_session_append as well. Both doesn't work. Also tried different CHUNK_SIZEs, but doesn't work either. Any suggestions?