I have been having the same issue since before the patch. For some reason, if I launch the tutorial to see if I can successfully launch the game before attempting a real match, I will not get this error. If I do get this error with the tutorial, I force quit the launcher and then try again until it works. Then I go into my regular game and everything works fine.
Here are my logs from the game it happened with tonight. It always gives me the error above, and then whenever I log back in to the launcher, I get to a screen that says "Game is still in progress..." with a 'Reconnect' button. Attempting to reconnect just gives me the same error as before, no matter how many times I try.