Issue after importing portal par file when Deselect the option to exclude portal content folders

In WebCenter Portal 12.2.1.3.0. I use Content Manager taskflow in one of my portal page.  I did the following steps:

1. In Dev, export portal by checking both "Include Shared Assets" and "Include Portal Content" checkbox. this include all my shared assets and folders and documents in content server;

2. import the par file to my local env by checking both "Include Shared Assets" and "Include Portal Content" checkbox. and make UI changes;

3. export par from local env by checking both "Include Shared Assets" and "Include Portal Content" checkbox.

4a, if I import updates par to Dev with both checkbox checked. import successful. portal works fine. but folders and documents in cs got overwritten.