Post excerpt is not always showing in widget

Hi there,
I have problem with this plugin. I have a few sidebars with this widget which is set to show 3 last posts from specific category. That works. I have also set it to show 30 words of excerpt to every post. And that works for most of them. But not everyone. Configuration of all these posts are the same (they have different dates of publish and content). For example it looks like this:

Post #1
date #1
excerpt #1 (read more #1)

Post #2
date #2
(read more #2)

Post #3
date #3
(read more #3)

Sometimes none of them have excerpt and sometimes – every post has everything correct. I have installed your amazing plugin on several sites and I have this problem for the first time.