Problem template blog articles

Hello everyone, I’m developing my new website with Grav and I’m learning to appreciate it more and more, but I’ve found a problem and I can not solve it.

Use as Quark theme developed by Trilby Media.

If in a blog article I try to set an image so as to preview it on the main page of the blog is ok, but if within the article begins the problem is as if the structure is corrupt, I tried to give a look in the code but everything seems ok (even if it is not).

Someone can help me, I leave a sample screen at this link.