Stuck at SONY logo

I did a Data Format on TWRP of my phone running Archidroid (First version of the Lollipop release) and then Factory reset it. After that, TWRP didn't boot properly at all! This is what I get when trying to reflash stock ROM
31/023/2015 17:23:05 - INFO - Selected Bundle for Sony Xperia M (C1905). FW release : 15.4.A.0.23. Customization : Generic PL
31/023/2015 17:23:05 - INFO - Preparing files for flashing
31/024/2015 17:24:42 - INFO - Please connect your device into flashmode.
31/025/2015 17:25:15 - INFO - Device connected in flash mode
31/025/2015 17:25:15 - INFO - Opening device for R/W
31/025/2015 17:25:15 - INFO - Reading device information
31/025/2015 17:25:15 - INFO - Phone ready for flashmode operations.
31/025/2015 17:25:15 - INFO - Opening TA partition 2
31/025/2015 17:25:15 - INFO - Current device : Unknown: May 9 2014/12:58:25 - YT910PACB2 - Unknown: May 9 2014/12:58:25 - Unknown: May 9 2014/12:58:25 - Unknown: May 9 2014/12:58:25
31/025/2015 17:25:15 - INFO - Closing TA partition
31/025/2015 17:25:15 - INFO - Start Flashing
31/025/2015 17:25:15 - INFO - Processing loader.sin
31/025/2015 17:25:15 - INFO - Checking header
31/025/2015 17:25:15 - INFO - Flashing data
31/025/2015 17:25:16 - INFO - Loader : S1_Root_dbe9 - Version : loader_MSM8X30_10 / Boot version : S1_Boot_MSM_8227_5 / Bootloader status : ROOTED
31/025/2015 17:25:16 - INFO - Transfer buffer size : 262144
31/025/2015 17:25:16 - INFO - Parsing boot delivery
31/025/2015 17:25:17 - INFO - You must have the according fsc script to flash this device.
31/025/2015 17:25:17 - INFO - Flashing finished.
31/025/2015 17:25:17 - INFO - Please unplug and start your phone
31/025/2015 17:25:17 - INFO - For flashtool, Unknown Sources and Debugging must be checked in phone settings
Any help is most appreciated and I am in quite a desperate situation atm :C Thx.

More info: It won't reach the bootanimation, It's stuck at the SONY logo only.
Device can do offline-charging with RED LED on
Flashmode is working with the LED turning on expectedly

I really hope this doesn't mean a bricked phone...