For me this duplicating bug is combined with another bug: whenever I use a previously taken photo to create an observation, the observation will have two photos: the one I wanted to use and an older photo, which I have previously used to make an observation on iNat. I wonder if anyone else has seen this behavior of iNat picking up old photos?
Anyway, I just sent a more detailed description and a fresh logfile to help@inaturalist.org, hope it helps.