Then:

• Start MSM download tool on computer (to flash stock rom)

• Push and hold the down etc for booting to EDL mode

• (while holding down the buttons) Plugin USB to computer

• (while still holding down the buttons) wait for MSMdownloadtool to recognize the phone

• Start the upload of the stock rom

After this my 6T was restored. Then I enabled the OEM unlocking again and the advanced reboot options. After that I was again able to unlock the phone and this time it didn't get stuck at the 'unlocked bootloader' anymore.

Hope it helps!

So I had the exact same thing, couldn't even turn it off, had to wait until the battery was depleted.
Then all I got was the battery low message, if I recharged the phone it would boot again to the 'stuck' unlocked bootloader screen wich it would show until the battery was empty again.

At first also the EDL mode didn't work, it got stuck on some sahara communication failed errror message.

In the end it helped te let the phone drain the battery completely until it goes off. Then, start the MSMdownloadtool while pressing the vp