Why am I getting demoted after 1 loss?

It's been a few times now that i have been demoted after a single loss at 0 LP, which makes zero sense to me. My friend went on a 6 game loss streak, AT 0 LP, and did not get demoted. Which boggles my mind, after 1 loss at 0 lp, on 3 separate occasions ive been demoted. Why? I thought you got a couple chances.

[sg-lux-2]