Error 255 in TWRP when making a Nandroid Backup

Hello friends !

So to install CM13 on my tab (GT-P5110) i need to make a Nandroid Backup.
Unfortunately, when at 75 % of the backup, the log of TWRP says me : E : createTarFork process ended with error=255
Any clues to resolve this issue ?

Thank you.