Duplicates Downloaded direct from camera

Another situation where duplicates can occur is if you shoot raw+jpeg and automatically stack the raw and jpeg files.  It is my belief that the Adobe Photo Downloader only searches visible files in the grid for duplicates.  So, if you try to import from a previously downloaded camera card and use the no duplicates filters, the jpeg files will be under the raw files in the stacks and the previously imported jpegs will import once again (with the -1 suffix). 

The easy solution to remove the duplicates is to perform a file search (Ctrl+Shift+K) for -1, and delete the files from the catalog (and your hard drive).

And just to be clear, are you using the APD filter to avoid duplicate imports?

There has been a few post about similar annoyances, like:

https://community.adobe.com/t5/photoshop-elements-discussions/elements-organizer-shows-two-copies-of-each-photo-from-my-iphone-when-downloading/td-p/12506493

When checking the different situations, it appears that the duplication exists in the phone or camera, so that the duplicates are imported ; since you can't have two similar filenames in the same destination folder, the OS adds a suffix to differentiate them.

The simplest solution: use a very cheap card reader instead of a cable.