Images and Internet Explorer

We are publishing our Xerte LOs using Javascript and our organisational browser is Internet Explorer (various versions; I am on 11). Since our move from Flash to JavaScript we now have the following issue - when the user first goes from our Moodle LMS into the LO, some of the images on the slides are outsized. If they click back to our LMS and then back into the LO the images all appear fine the second time around. Firefox seems to be fine...Can anyone advise? Thanks