Description:
When I create a list and put a style of List1 to the list the bullets shown are normal and well formated. I can save the document, as default docx, and continue finely until the document closed.
However when I close document and reopen the document the bullets appear fatter/thicker and when I check their style & formatting it is changed from List1 to WWNum1 or WWNum2 or...WWNumx. 

I am using following version of Liber office 
Version: 6.0.1.1
Build ID: 60bfb1526849283ce2491346ed2aa51c465abfe6
CPU threads: 4; OS: Linux 4.13; UI render: default; VCL: gtk2; 
Locale: en-AU (en_AU.UTF-8); Calc: group

The OS I am using is Ubuntu 17.10




Steps to Reproduce:
1. The Writer default save should be set to docx format
2. Create a new Writer document 
3. enter a list of words in consecutive lines
4. Select the Dropdown of Styles
5. Open More Styles Go to the list Styles
6. Select List1
7. Save the document as docx( default set as docx)
8. Close the document
9. Reopen Document to see the bullets changed to fatter bullets and when you check the Styles & Formatting > List Styles the style shows "WWNumx" style where x can be 1, 2 ....n

Actual Results:  
 Reopen Document to see the bullets changed to fatter bullets and when you check the Styles & Formatting > List Styles the style shows "WWNumx" style where x can be 1, 2 ....n

Expected Results:
The List1 formatting should be retained


Reproducible: Always


User Profile Reset: Yes


OpenGL enabled: Yes

Additional Info:


User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:58.0) Gecko/20100101 Firefox/58.0