Hallo,

after updating the Template (Fontaine von arrowthemes), all K2-adjustments were lost.
Only the set K2 image-attitudes will not overtake (all Image-widths to 100%),
But all works with the protostar-Template.

Regards, Martin

Mayday! Mayday! We are gaining attitude!

All jokes aside, since you say it works with other themes, it sounds to be that it's theme-related.
One potential solution could be to place the img-attributes higher in the css (if you use this).

this was the solution:

.catItemImageBlock img, .itemImageBlock img {
width: auto !important;
}

That's usually a solution, pushing it forward by using !important. Glad you found the solution!important