Error code 13 with unraring large files

Hi,

Everything is in the title!

using KEKA, on large files, i got this error code when i try to unrar them.
it's 15 rar files of 5,5GB each.

I also noticed something strange. When i try to unrar with the Unrar X application, it telles me: not a rar files. which is really strange because other people succeed in unraring them all!

i got this problem only on large files and at every state of progress.. Something it happen at 5% after start sometimes 40% sometimes 55% etc... any time.

i try to unrar them on 4 différent HD on 2 different computers.