Problems with a % character in a Post Title

Hi folks,

I have found a problem when I add a % character in a Post Title.

When I write a post with the Title: e.g. “New 10% Increase”
The Preview Snippet renders that as: “New 10post_author_firstnamepost_author_lastname% –
And the Title box below reads in red, “86 characters.”

When I take out the % sign from the Title: e.g. “New Increase”
The Preview Snippet render is correct, as: “New Increase” by ….
And the Title box below reads, “13 characters.”

This the first time I have tried to use this character in a title, so I don’t know how long it has been a problem.
FYI, I have not checked other characters to see if there are other such issues.

Regards and thanks,
Angus