Sharer might show incorrect image and other meta tags content if meta tags are not present in the HTML source of your website and/or meta tags cache needs to be purged.

You can do following things to fix this problem:

If Open Graph Meta Tags, Twitter card tags and other meta tags are not present in the HTML source of your website, you can install Heateor Open Graph Meta Tags plugin. This will insert proper meta tags in the HTML source of your website.

If you still face the same issue, then you need to clear Open Graph Meta Tags cache by navigating to url https://developers.facebook.com/tools/debug/og/object/. Paste the url of problematic webpage in the textbox at the link and click the Fetch new scrape information button.