The layout.master file of the skin has attributes on the <portal:ScriptLoader that tell it to load the script from /ClientScript/jqmojo/jquery.imagefit.min.js
that would be the script that resizes images to fit the screen, it is an older version of imagefit, you could try backing up the file and replacing it with a newer version which you could find via google if you confirm it to be the cause of the problem.
possibly width and height attributes in the raw markup before the js runs may be a factor in what the js does when resizing images.