Penalized SR for teammates leaving


I was just in a competitive match at about 1830 SR, when my teammates became toxic and one of them eventually left. I don’t necessarily know how the system responds to people leaving in a comp. match, but recently the same thing happened at the beginning of a game, and i was prompted that if the player that left didn’t rejoin in about 30 or so seconds, that everyone would be removed from the match with no affect on their SR. However, in this match, I was prompted with a message that said that if I left during the timespan it read, that I would be penalized; I proceeded to lose the first round. When I looked at the team when I was choosing a hero for the next round, I saw that another player had left, but the message had dissappeared (I wasn’t sure if it ran down, but i’m going to assume that it did). I was told by another player in the match that I could now leave without any punishment, so I did, and when I looked at my SR, I dropped about 30 points.
I’m not sure if this is a bug or not, and I’m not demanding that I be given the SR that I lost. I only want someone to explain what happened and how I was involved, so that I can avoid this happening again in the future. I havent tried playing another match so i’m not sure if I was banned or not, but the card still says that it’s available.
I just don’t think that this would be programmed in, to penalize everyone in the team for just one person leaving. Whenever I gain, it’s only about 15-20 points, so to lose this much is an unnecessary set-bakc.
Thank you for reading.