I’m having the same problem. When I put the following into the Yoast > SEO > Titles “Post Title” field:
%%title%% | %%sitename%%
it shows ‘Post Title | Sitename’ in the Snippet preview, but the actual page title comes out as ‘Post Title | Sitename Sitename’
After some experimenting on other sites, I think I narrowed the problem down to an issue with previous settings using the All in One SEO plugin. On sites where I had used All in One SEO, then imported and deleted the previous plugin content, this behavior happens each time. It may be drawing some redundant cache from the database, but it happens on new posts as well as old ones.
The workaround I use until Yoast can fix this is to use the following in my Title fields:
%%title%% |
Note the space after the separator to ensure that this extra sitename pushed into place doesn’t crowd the separator character.
Hoping Yoast can fix this soon.