Using %%exerpt%% in meta description template results in wrong SEO analysis

I have noticed that when I am using %%excerpt%% or %%excerpt_only%% as the template for the meta description, the SEO analysis shows wrong results:

1) Keyword not found: Although my keyword is included in the excerpt / meta description (and is shown in bold in the snippet preview), the error “A meta description has been specified, but it does not contain the focus keyword” is shown.

2) Wrong text length: Even when the length of my excerpt is longer than the suggested 156 characters, the error “The meta description is under 120 characters, however up to 156 characters are available.” is shown.

Both of the issues above do not occur if I copy and paste the excerpt manually into the meta description field of the snippet editor.

Thanks for looking into this issue.

https://wordpress.org/plugins/wordpress-seo/