Content layout not consistent

Hi, I just use catch-box theme for my new site. In the theme option I choose "show excerpt" for the content layout. But the content layout become not consistent. Some posts can show only summary which is consist of title, meta box, post thumnail, 40 words excerpt and tags box. But the other posts show the full content of post which is very annoying. What should I do to fix this problem? Thanks in advance.