I have been using Dropbox for years and have changed my mobile phone several times with no problem however last December I upgraded my Samsung Galaxy S9 to a Samsung Galaxy S21 and took some pictures and when I started to download them to Dropbox although I had only selected the most recent files what happened was that all the pictures on my phone (which had been transferred from the old phone) and which had already been downloaded to Dropbox were being downloaded a second time until my Dropbox was full.
I then had to delete all the duplicates to free up space on Dropbox. This put me off doing this on my phone but the other day I took some more photos and when I started downloading them to Dropbox the same thing happened. This is infuriating and never happened previously when I changed my phone. Can anyone spot what is going on here and how to stop it?