This is very strange.
Whenever you rename a page/post title, it should reflect this same title in the Pages section of the assignment panel. Have you tried to refresh and clear you browser cache? Also are you using CJT on a WordPress Multisite installation?
Please explain further and tell me what you have tried and what are the results.
Both pages with similar heading and the fist 15 Chinese characters are the same, I think the page list only show the first 30 characters rather then the whole, so that’s why I see the same title with different URL.
It is not a big issue, but if the page list can show first n characters and last n characters will help to distinguish the difference.