Hi - I'm having a similar problem with my site, it is looking fine on mobile and desktop, but on tablet (mainly portrait) the fluid layout is really messing with the aspect ratio of the image.
I am using the fill setting as my image borders would not look effective with any padding in the fit option.
Is there anyway I can limit the lengthening/aspect ratio changes that are happening with viewport size changes? I need a sitewide fix rather than blocks if at all possible as it's for a template.
Below I have attached screenshots of an example (second photo is the issue), but the problem is happening throughout my site.