Hi, annoying bug here that was also present in PHotoshop 2024. I just updated to 2025 and the issue is present.
To reproduce:
Select 1 or more artboards
Hold Opt/Alt, then drag artboards to duplicate
after several seconds, duplicate artboards appear as expected, then a bit later a second artboard or artboards will appear inthe direction you dragged, as if you had dragged it again. You can undo once and it undoes the second instance of duplicate artboards.
It's not totally consistent, I think it may have to do with artboards containing objects that are larger than the artboard, maybe objects that would overlap with other artboards if they werent already contained in an artboard.
I've found this on Windows, but not Mac.