Wordpress page title repeated in SOME pages

Question

I have created a Wordpress site and titles were working just fine. Then, some time and plugins installed later, I noticed that in SOME pages I get the title repeated 2 times.

Example of wrong page title: Contact - NAME | NAME

Example of normal title: Our Services | NAME

Now, if I go to General Settings and change title it will change both, no improvement. SEO by Yoast has the option to reset page titles, but that just removes all titles leaving the current URL as page title, so no good either.

Here is the code I originally had: <title><?php wp_title(''); ?><?php if(wp_title('', false)) { echo ' | '; } ?><?php bloginfo('name'); ?></title>

Here is the code I am using now: <title><?php wp_title('|'); ?></title>

To sum up, I think somewhere in the database there's a wp_title repeated: once using '-' as separator, another one (the current one) using '|'.

Any help will be most appreciated, thanks!