I have solved it. It was something related with cache. Topic solved.
I have the plugin. I changed the height to 300 px and then I have regenerated the thumbnails. I have even recreated the Logo/Partner list element. It is the same. Images are cropped.:(
I solved the problem. I looked in HTML code and I observed I have pasted some CSS code along with the title in the toggle shortcode. That was the cause of not displaying it correctly. Once I checked out the quote marks I discovered my error.
Thank you for your help. The topic is closed.