I’m describing a situation such as where I click photo 1 and shift-click photo 10, it should highlight 1-10, but instead it highlights something like 1 and 30-40, or 1, 5,7 and 10. Effectively it seems to be incorrectly highlighting the ranges.
duplication can have the same effect as reordering because the duplicated observation by default will be placed immediately after the source observation in the upload page. for example, if you create obs A and obs B, and then you duplicate obs A, the dupe A will show up between obs A and obs B. in other words, the dupe A will be the third observation created on the page, but it shows up as the second observation visually.
so your case would be the same issue as described in the second bug report i noted above.