DVR not exporting to usb

hi guys

please i need help with this challenge i am currently experiencing with a client's device. It's a DS-7232-HGHI K2 model with V4.30.101 firmware, it doesn't export footage to a external storage device; flash or disc, initially it starts backing-up then all of a sudden it stops and doesn't save in the flash.

i've attached a picture of it..

thanks in anticipation