Android app : 60GB of photos gets duplicated on my cell phone

When I setup an automatic upload for my photos with Nextcloud app on android phone, all the photos and videos gets uploaded to the server but also downloaded or copied to another folder on the phone (/storage/emulated/0/Android/media/com.nextcloud.client).
I’m about to go mad trying to fix this problem. I googled, and googled, and I found only a couple of cases like this with no fix.
Unless it’s something really stupid, I find it hard to believe that I’m almost the only one experiencing this.
Thanks in advance for any help.