@sellew - This doesn't surprise me. I believe I saw this as well when testing, but it was infrequent enough not to risk any more changes after finally getting it working
It could be signals getting lost, timing issues of updating the location before the file load is complete. I've made a note to look into it again.
@mrmikel - I've also seen this - where the externally edited image is not updated. You need to close the tab, open the image it its tab, then re-open the html file and it usually displays ok, but not always. Reloading the book will fix it though. Something with the caching of images and timing of signals/updates as well, but not related to the issue above. Annoying any fix that was tried made things even worse if Preview was open. It doesn't help that the timing/signals on Win 7 and Linux seem to be so different. Also on the list.