Hi,

It's not a bug. This issue caused by your post content.

Example:

When you write a sentence:

we're going swimming  => WordPress will understand you have 3 words in this sentence - separated by a space.

But, if you write a sentence:

I go out => WordPress still understand you have 3 words in this sentence.

And if you compare:

we're going swimming

And 

I go out 

You can see the sentence "we're going swimming" much wider and longer with "I go out".

It happens the same with your excerpt now. The excerpt on the post "Hope for the dogs of oaxaca" has wider and longer than the excerpt from the post "A place woven with traditions" - so it drop to a new line.

And this is normal

Best Regards,

PenciDesign