E2303 cannot be downgraded from 26.1.A.3.111

Hi all
I'm trying to downgrade a M4 aqua with the new firmware (26.1.A.3.111) with flashtools and I've issues with the bootloader. The error is this:

20/059/2016 07:59:35 - INFO - Current device : E2303 - YT9113NU6R - 1293-9383_R4A - 1291-5963_26.1.A.3.111 - GENERIC_26.1.A.3.111
20/059/2016 07:59:35 - INFO - Start Flashing
20/059/2016 07:59:35 - INFO - Processing loader.sin
20/059/2016 07:59:35 - INFO - Checking header
20/059/2016 07:59:35 - INFO - Flashing data
20/059/2016 07:59:35 - INFO - Processing of loader.sin finished.
20/059/2016 07:59:35 - INFO - Loader : S1_Root_54c8 - Version : MSM8936_14 / Boot version : S1_Boot_MSM8939_LA2.0_37 / Bootloader status : NOT_ROOTABLE
20/059/2016 07:59:36 - INFO - Parsing boot delivery
20/059/2016 07:59:36 - INFO - Phone boot version : S1_Boot_MSM8939_LA2.0_37. Boot delivery version : S1_Boot_MSM8936_LA2.0_30
20/059/2016 07:59:36 - INFO - Going to flash boot delivery
20/059/2016 07:59:36 - ERROR - missing
20/059/2016 07:59:36 - INFO - Some files are missing from your boot delivery

I've check several root tutorials and they skip this step because boot delivery version are the same. If I flash the terminal without changing the bootloader, the phone enters in a bootloop or the initial setup is not finished. I have tried with both 2.128 and 2.112 firmwares. Any suggestions to root my terminal?

Thanks in advance

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