Twrp backup fail (external storage/usb_otg)

[4rsenal]

So I'm trying to make a backup on TWRP through external storage ( I tried through both a SD card and a USB_OTG) and I get this fail message.. any ideas? Is it a format issue?

 

[Krystalmyth]

This has been happening to me too. No idea why.

 

[Adabow12]

Any new info on this? I am getting the same failure on system image.