Thanks for the response.
I did see the functions.php but the thumbnail size is not the problem, rather what is being shown, cropped, is.
What I'm wondering is why is the media library edit image crop is not showing in the Theme? WP does the crop in media library and if you go to media tab when setting up the featured image, the small thumbnails in the list of images look as they should (the way I cropped them in media library edit image crop), but once I select an image and publish the post, the featured image thumbnail is different, read it looks the way WP and/or Theme "likes" to crop it (seams like centered crop to predefined size). So Theme is discarding the crop done in the Media library edit image.
I have also tried the link you've sent and it is not making any difference, the images for thumbnails are still being cropped with predefined rules and nothing you do in WP interface is going to changing it.
I did notice in the previous WP version there was a hard crop function when setting up the thumbnails, does this have to do something with the problem we are facing?
I would really appropriate you helping us solve this issue sine it is really paramount that we can define whats being shown as thumbnail (crop them in a visual way, let them keep the ratio and size that is not important but what we see in many cases must be different from the predefined centered crop).