Hi Linda,
I tried this and note that the Fit-to-Contents does not size correctly with odd pixel images. The image looks fine...just that the boundary box is one pixel extra. I don't get it moving around the page, but I may not be setting things up the same as you.
With your experience I've guess you've already tried this, but what happens if you use "Fixed" on the Image Properties tab, instead of "Scale to Fit"? (I'm hoping the former may be a solution for you)
Which transition are you using to 'dissolve' the image?