It would appear that the orientation of the images is what's causing it to shift positions. Notice that the bracelet is horizontal in the one where it's under the ring and vertical when it's pushed to the side. Can't tell you why but maybe that will lead you to an answer.
If you look at each with a browser inspector, you'll see that the css is not the same. One has a float:left while the other doesn't. There are other differences too. Also there's an inline 'width' specification that is bad in that it's coming out as 'width: px'.
Suggest you work with the theme provider to resolve any differences and/or review any tweaks you may have made to the theme's css in the store with the thumbnail gallery on the left.