Not sure, I know that I've played some MOTD solo lately and when I do that, if the key is not outside the cafeteria, I quit and restart, that is all on round one. I've had to do that like 5-6 times recently to get the game started and didn't get de-ranked for it.
This is of course after feeding the first dog 5 z's, so maybe the 5 z's that I am killing is enough to maintain the rank. 
??? IDK, all I know is that it hasn't happened to me.