Twrp back up problem

[hazatree71]

Hi there,
I am trying to do a back up using file TWRP-3.1.1-0-picassowifi.img.tar installed on my samsung galaxy tab pro 10.1 sm-t520 prior to installing a custom rom.
The problem I am having is that evertime I try to run the twrp backup it gets to at best about 41% and then the backup drops out and the tablet restarts in normal mode. I have tried 2 different Sandisk 32gb SD cards but get the same results each time.I have trawled around the net but cant find anything to point me in the right direction.
If anyone could point me in the right direction that would be great.

many thanks
hazatree71

 

[ocnbrze]

try wiping cache and dalvik cache and then restore your backup.