I don´t know what You are doing, I just know what I do 
It did not work. It only restores to the original source and gives no option to select an alternative destination. Is it possible to use a regular SD card in an adapter and boot the box from a USB port? I ask because I just discovered that the micro SD card I wanted to clone to has a max read speed of only 30 MB/s and the only one I have left is a SanDisk 64 Gb Extreme Pro SD card. If I can use that it has a 200 MB/s read speed.
Edit: I tried it and it won’t work. I am going to have to order another micro SD card.
The SanDisk is perfect . You only need 8Gb. I use 32 and 64.
I always use the Coreelec back up under system in Coreelec settings.
I save the backups on my win pc from … \\192.168.0.14 (my CE ip in win explorer).
For a new install I use Rufus and make a new Coreelec sd using the version or nightly I want.
I insert into box and setup. I then put my prev saved CE backup into the backup folder using addy above and restore.