I've been demoted unexpectedly

Today I have around 170 rank points at Silver 2 and then I get a win after this. So I had 370 rank points. After that I lost a game and the game demoted me immediately to Silver 3, 800 rank points. Is this normal? Btw I have 29 wins 26 loses.

Been demoted many times due to game crashing before entering the picking phase, that’s just free punishing because Blizzard hates their players.