Magento 2 Shipping – Table Rates Always Zero When Adding More Items

I'm using "weight vs destination" and I have imported the csv successfully. I have checked the "shipping_tablerate" table and the data is correct.

When I added an item with weight = 1.00 to the cart, the shipping fee is correct. However, when I added another item with weight = 1.00 or added the same item again, the shipping fee is always zero. Why?

I'm using Magento v2.1.1 CE.

mysql> select * from shipping_tablerate where website_id = 1 and dest_country_id = 'HK';
+----+------------+-----------------+----------------+----------+----------------+-----------------+--------+--------+
| pk | website_id | dest_country_id | dest_region_id | dest_zip | condition_name | condition_value | price  | cost   |
+----+------------+-----------------+----------------+----------+----------------+-----------------+--------+--------+
| 31 |          1 | HK              |              0 | *        | package_weight |          0.0000 | 5.5000 | 0.0000 |
| 30 |          1 | HK              |              0 | *        | package_weight |          1.0100 | 6.5000 | 0.0000 |
| 29 |          1 | HK              |              0 | *        | package_weight |          2.0100 | 7.5000 | 0.0000 |
| 28 |          1 | HK              |              0 | *        | package_weight |          3.0100 | 8.5000 | 0.0000 |
+----+------------+-----------------+----------------+----------+----------------+-----------------+--------+--------+
4 rows in set (0.01 sec)

My CSV file:

Country,Region/State,"Zip/Postal Code","Weight (and above)","Shipping Price"
HK,*,*,3.01,8.50
HK,*,*,2.01,7.50
HK,*,*,1.01,6.50
HK,*,*,0.00,5.50