Have you tried wiping the cache partition on your device?
I managed this issue download all my picture and video contents using https://support.samsungcloud.com/, switch back to my mobile -> samsung cloud -> delete all data from cloud then create a new folder inside DCIM folder with all photos download on my computer..
After that the samsung cloud start to sync from scratch fixing it.
Don't know the root cause but it seems the Samsung cloud database got corrupted and I believe it is related to a picture dated to Sep-2700 I got in my mobile
Give these steps a try: Go to settings > accounts and backups > Samsung Cloud > Gallery> and is the sync option toggled on? If it's toggled on Go to albums to sync and can you tell me what is toggled on?