Hope I am not too late, I found a way around this.
What I did was downgrade from Marshmallow to Lollipop.
I did it by using the LGUP program and following this:
In short what I did was:
1. Download the kdz
2. Download LGUP and install it, then the dll thing that comes in the archive.
3. Install LG drivers
4. Put device in download mode by pressing up and inserting a usb cable when device is powered off
5. start LGUP and select "Refurbish"
6. in the path select the kdz (even though its looking for tot files).
7. Flash Lollipop and boot
8. Go back to download mode, now you have Send_Command.exe
Then I flashed "H815L 10F.kdz" which gave me stock Lollipop on 815L. I am not sure where I got it, It was sitting on my disk. But basically anything which has H815L (for the model), and 10 which means its Lollipop should work.
Then I could go in to download mode and run Send_Command.exe