Unable to upload maps via ROS service

This issue happens with firmware version augmented-lidar-os_5.1.0-alpha2 of ALB.
To reproduce the issue:

1. make sure there is a valid ply file: /my_directory/my_map.ply

2. call ROS service /alb/storage/upload with proper parameters:
   rosservice call /alb/storage/upload maps test_map.ply /my_directory/my_map.ply
   The service replies with:
   success: True
message: "File successfully uploaded."

3. call ROS service /alb/storage/list to get all the maps:
   rosservice call /alb/storage/list maps "" "/my_directory/maps_storage.json"
   The service replies with:
   success: True
message: "Files successfully displayed."

4. In the file maps_storage.json, the test_map.ply map shows size of 0. And from the ALB web interface, the test_map is not in the map list:
   { "category": "maps", "mtime": "2022-02-03T11:36:21Z", "name": "test_map.ply", "size": 0 },