I'm getting a wierd error while trying to downgrade.

Ok so I'm trying to downgrade my XSP since it's just painful to use it on 4.3,way too many bugs.
But I get this error when I try to flash a generic 4.1.2 ftf.
20/052/2014 07:52:10 - INFO - Selected SP-C5303 / 12.0.A.2.254 / Generic UK
20/052/2014 07:52:10 - INFO - Preparing files for flashing
20/053/2014 07:53:07 - INFO - Please connect your device into flashmode.
20/054/2014 07:54:01 - INFO - Device connected in fastboot mode
20/054/2014 07:54:06 - INFO - Device disconnected
20/054/2014 07:54:13 - INFO - Device connected in flash mode
20/054/2014 07:54:13 - INFO - Opening device for R/W
20/054/2014 07:54:14 - INFO - Start Flashing
20/054/2014 07:54:14 - INFO - Processing loader
20/054/2014 07:54:14 - INFO - Checking header
20/054/2014 07:54:14 - INFO - Ending flash session
20/054/2014 07:54:14 - ERROR -
20/054/2014 07:54:14 - ERROR - Error flashing. Aborted
I used factory reset and locking and relocking the bootloader but nothing helps.
So..is there any way for me to downgrade?

How do I flash a 4.1.2 rom that requires 12.0.A.2.254 ?
I'm kind of a begginer with the flashing and everything.