Att D850 no download mode, rims fail flashing in TWRP!

[lankyboy28]

Hello,
Got a couple of weird things with Att d850.
What Ive done:
-Downgraded using lgup mm to kk
-rooted using king root
-flashed recovery using autorec
-using twrp flashed a rom wrongly that was for the d855
-it kept rebooting so i wiped and tried flashing other roms to no success
-download mode gone
-ive tried pushing almost all the .img files through fastboot(including laf.img) no success.
-im on twrp now, no download mode and I cant flash any roms. Every rom I try now it throws the following error:
“e error executing updater binary in zip '/external_sd”
-after each flash try the system gets unmounted and i have to fix/format the internal ext4 (maybe wrong description). Mount works again.
Any advice?
Thanks,
Chris.