I'm trying to backup my system using Remastersys 2.0.12-1. There is no problem during the ISO file creation period. After creating the ISO file, I've install that on my USB drive using UNetBootin. Everything is successful, but problem ocuurs just duing boot. Boot menu appears perfectly, but when I press enter, then it shows the following message

Could not find ramdisk image: /ubninit
I can't understand why this is happening. I've used Remastersys before, faced no issue then, but this error is happening again and again.

Experts help me please. Need to solve this quickly.

Thanks in advance.