How to fix 404 errors in GWT?

[Divvy]

Since last month, I see a huge increase of 404 errors in my website that doesn't make sense.

For example:

404 ERROR URL: https://domain.com/post-title-here/titlehere6/

<a href="https://domain.com/wp-content/uploads/2015/10/titlehere6.jpg" title="titlehere6" rel="wpsimplegallery_group_3201"><img src="https://domain.com/wp-content/uploads/2015/10/titlehere6-150x150.jpg" width="150" height="150" alt="titlehere6" data-pagespeed-url-hash="1383918117" onload="pagespeed.CriticalImages.checkImageForCriticality(this);"/></a>

FROM: https://domain.com/post-title-here/

URL: https://domain.com/post-title-here/name-fb/

<meta property="og:image" content="https://domain.com/wp-content/uploads/2015/10/name-fb.jpg"/>
<meta property="og:image:secure_url" content="https://domain.com/wp-content/uploads/2015/10/name-fb.jpg"/>

FROM: https://domain.com/post-title-here/

Any idea of what could be?

It seems that is grabbing the image title and put in front of the url:

domain.com/post-title-here/imagetitle

Any idea of what could be and how to fix it?
Please PM me if you want to see website code source.

Thanks!