hair particles, mirror doesn't work.

Hello. Thank you for watching.

If I select all of the hair particles and mirror it, most of the hair is mirrored, but some of the hair near center aren’t be mirrored.
Why is this and how can I fix this?

hair.blend (736 KB)


I’m going to conclude this as a bug.
The solution is tu just turn on X-mirror and manually add hair around there.