I agree that booking can be random sometimes , but the manager can increase the risk of it by playing in a certain way ( usually a wrong way ). For example if you play with hard defensive + hard tackle+ mtm is a suicide you will get cards for sure, penaltys and also red card if oppo have very fast players that can dribble past and the only way to stop them is a foul. I always go hard on tackles but i get 1yellow card every 2 games( rarely red , last i remeber is like 2 seasons ago ), they asked me how do you do that ? just make lot of possesion, if your players have the ball they will not need to make fouls is simple, in fact my oppos instead usually get a red card, is a style of play. So what i'm trying to say is that the manager instructions can influence the team getting cards, but sometimes your player will be in a bad mood and boom.. double yellow or direct red