League-wide fumble and penalty rates between Sandbox and the NFL are similar. Both data sets are easily available and you can compare for yourself. Some penalties that are similar in nature are grouped (e.g. face mask, horse collar, unnecessary roughness, tripping, late hit and a bunch of others are lumped together as personal fouls).
Kevin and I are Chiefs fans and neither of us will ever forget the “no-punt” playoff game against the Colts after the 2003 season. Over the previous two seasons Priest Holmes had carried the ball more than 600 times for more than 3000 yards with only 2 fumbles. Yet we arguably lost the game because Priest Holmes fumbled in that game. There are hundreds of incidents like this. Sometimes the random stuff determines the outcomes of games. It is frustrating as an NFL fan and frustrating as a Sandbox owner — but it is an essential part of the game.