What triggers this issue?
This issue reports indexable pages with more than one title tag.
Why is it important?
The title tag gives users and the search engines an idea of what the content of a result is about and how it’s related to the search query. Other than that, titles play a significant role in whether a search result is clicked on or not. This is why you need to make sure your title tags are as informative as possible.
Should there be more than one <title> tag, it can cause some confusion for search engines with picking the right one for the page. Also, multiple <title> tags might alarm Google’s algorithms as a black-hat SEO trick to target more keywords.
If search engines pick up a non-relevant <title> tag, it can mislead users and result in high bounce rate which, subsequently, is harmful to rankings. Ensure that each of your pages has only one title tag, and it’s relevant to the pages’ content.
How to fix it?
There can be various reasons as to why your pages have multiple <title> tags. Sometimes, it’s caused by malfunctioning or misconfigured plugins or modules in your CMS.
In this case, review your settings and make sure that no error crept in. Consult the developers if needed.
Alternatively, you might have added several tags by mistake, for instance, after A/B testing. If so, delete the excessive ones.