If you still have working ROM try what is suggested here:
Since you have working ROM, try to flash that small update.app with normal update process via System updates-Update from SD card, if 3 button method fails.
I had the same.
I put it in dload that: http://dl.vmall.com/c01l4l4a2y# via local update, after that you can flash 4.2.2 without issues again via local update.
Another link for the download in case it is slow from the first one https://mega.co.nz/#!9oEHUTiR!uVKEq6...QZ5yrnedx4rug4
I managed to get back to 4.2.2
Now I installed 4.2.2 b610 vodafone dload method.
Boot and recovery are 4.2.2? or have something old? How can I check?
So i tried to wipe cache, data and dalvik cache on twrp 2.7.0.0 and rebooted into bootloader and flashed the stock KK recovery from the thread.
Then i booted my phone up into the stock recovery and it tried to flash the B506 dload with the same error.
I also tried to flash the small update.app without success