[Galaxy S6 Q&A, Help & Troubleshooting] Malganor:
Hi, sorry to revive this old thread but the situation is similar to mine. My situation and how I got there: I got a hand-me-down S6, model G925W8, and wanted to remove as much of the bloatware on it so started by rooting it with it's appropriate root file from here "https://autoroot.chainfire.eu/" and applied it through Odin. I then installed TWRP ver. 2.8.1.7 from here "https://dl.twrp.me/zeroltetmo/" also through Odin. I then installed XtreSoLite through TWRP and after I installed some of the Aroma addons from "http://xdaforums.com/galaxy-s6/development/rom-xtrestolite-pure-edition-1-0-beta-1-t3082467".

The issues began when I attempted to encrypt the device with the vanilla encryption method, without a the quick encryption method selected if that helps, and was stuck on a black screen for a long period of time until I rebooted via "Volume down + Power key". The device then restarted, showed an "Encryption Failed" screen, and offered to reset and wipe the phone to continue, as the only option, but when I accepted it simply rebooted, brought up TWRP for a second, and returned to the Encryption Failed screen. I tried wiping the device to factory defaults via TWRP and still the device booted to "Encryption Failed". I then wiped as much of the phone as I could, including the cache and other parts and ended up with a phone with no OS and no TWRP. Reinstalled the root, TWRP, and used ADB to copy XtreSoLite back on the device only to return yet again, after all that, to a "Encryption Failed" screen. Before adding XtreSoLite a second time I also tried to return to android stock from here "http://xdaforums.com/galaxy-s6-edge/general/canada-galaxy-s6-edge-canadian-users-t3069314" but that failed to even get as far as the Encryption Failed screen.

I found this post but when I tried to follow the link for firmware and "pit" install I end up at an error "http://samfirm.net/post/129549796737/pit-file-galaxy-s6" there as the page no longer seems to exist, assuming it was applicable to my situation. As it stands, I have exhausted all of the few options I know about as I am very new to flashing and rooting android devices and this is my first time doing so. I want to get past the Encryption Failed screen and after that find out how to encrypt my rooted device properly but the primary issue is still the most important one - getting past the Encryption Failed screen. Any assistance provide would be amazing and I do apologies in advance if I missed something obvious. Thank you!

EDIT: Went the way of trying another stock rom from here "http://xdaforums.com/galaxy-s6-edge/general/sm-g925f-s6-firmware-thread-t3078841" for my G925W8 then got "NAND Write Start!! FAIL!" so grabbed a pit from here "http://xdaforums.com/galaxy-s6-edge/general/g925-pit-files-multi-thread-download-t3171636" for my model and followed the instructions here "http://xdaforums.com/galaxy-s6-edge/help/guide-s6-edge-unbrick-guide-t3187655":

"..3) Find the corresponding .PIT file for your S6 EDGE.

4) Find the corresponding stock rom for your S6 EDGE.

5) Then put them into odin CORRECTLY. Rom to "AP", .pit to PIT

6) Make Sure these are checked: "Re-partition","NAND all erase"

7) Plug your device in and then press start."

And got this read out:

"<ID:0/007> Odin engine v(ID:3.1005)..

<ID:0/007> File analysis..

<ID:0/007> SetupConnection..

<ID:0/007> Initialzation..

<ID:0/007> Erase...

<ID:0/007> Set PIT file..

<ID:0/007> DO NOT TURN OFF TARGET!!

<ID:0/007> Get PIT for mapping..

<ID:0/007> Firmware update start..

<ID:0/007> SingleDownload.

<ID:0/007> sboot.bin

<ID:0/007> NAND Write Start!!

<ID:0/007> FAIL!

<ID:0/007>

<ID:0/007> Complete(Write) operation failed.

<OSM> All threads completed. (succeed 0 / failed 1)"

So still got a NAND write fail...

Edit 2:

Tried pit/stock rom a few more times with no success...had a suspicion that the custom rom would still work and tried my previous methods and I can load XtreSoLite now. But not stock...lulz. No NAND write issues on anything except stock roms for my device...although I tried two seperate stock ones from links given here. Now, just got to figure out how to encrypt a rooted device...