acces denied: images in a ftp-prog like filezilla

Hello,
A strange thing!
In Filezilla I cannot download my images (as a backup). I uploaded them myself in Enfold. Enfold (or WP) makes a dozen variations in size of each image. When I try to make a backup of all files of the website by using a FTP-program, all those variations in size of the images I can download, but the original images not. It says “acces denied“!! This problem exists NOT in the directories before february 2015. Strange!!
You will say: “Well what’s the problem. Those images you uploaded yourself and are not downloadable? You have them on your local desktop! So, why bother?”
That’s right! BUT I try the use a backup-plugin like “Duplicator“. Duplicator gives and error and stops functioning, because acces is denied at some lousy images!

Can you help me?

Regards

Jan-Hein de Wit (Blauwoog)