i think the problem in CUST partition.I wanted to try the b839 but Im not able to get the local update to work. With forced update the update process just fails right at the beginning.
Since there seams to be a problem with local update with TWRP I flashed stock b830 recovery ( b851 not available) but it still fails to update.
I tryed with different update.app (B800, B830, B609 full firmwares) files which worked before without any problems.
Any Idee why it wont work?
Furtunately, B851 stills runs good.