Default Help plz I9505 stuck in bootloop

Hi,

tried to flash the 4.4 stock on my I9505 (was on 4.3, which worked fine).

4.4 didnt run smooth so I restored the old backup and ended up in a bootloop.

Tried to flash Samsung 4.3 stock via Odin but it fails every time giving me this message:

<OSM> Enter CS for MD5..
<OSM> Check MD5.. Do not unplug the cable..
<OSM> Please wait..
<OSM> I9500XXUAMDK_I9500MBCAMD6_I9500XXUAMDK_HOME.tar.md 5 is valid.
<OSM> Checking MD5 finished Sucessfully..
<OSM> Leave CS..
<ID:0/005> Odin v.3 engine (ID:5)..
<ID:0/005> File analysis..
<ID:0/005> SetupConnection..
<ID:0/005> Initialzation..
<ID:0/005> Get PIT for mapping..
<ID:0/005> Firmware update start..
<ID:0/005> boot.img
<ID:0/005> NAND Write Start!!
<ID:0/005> recovery.img
<ID:0/005> system.img
<ID:0/005> FAIL!
<OSM> All threads completed. (succeed 0 / failed 1)

any suggestions? Would be very happy!