I normally drive in L mode. When you take your foot off the accelerator pedal, the car slows and then comes to a complete stop. The car will remain stationary even if you are on a slope, without having to press on the brake.

I was on level ground stopped with my foot off the brake in L mode. Suddenly the car thumped and jolted forward harshly exactly as if someone hit me from behind. But when I looked behind me there was no one. Then, the car took off "idling" forward like a gas car will do in Drive if you don't hold on the brake. I had to stomp on the brake to prevent hitting the car in front of me. I looked at the dash and the shifter and confirmed the car was in L mode. The car continued to act as if it was in D mode until I shut down the power and powered back up. Later that day it happened again, only this time there wasn't a harsh jolt like the first time. The car just randomly started moving forward quickly as if it were in D mode.

This forces me to have to hold my foot on the brake when stopped even in L mode for fear that the car will suddenly lurch forward unexpectedly, causing me to hit the car in front of me.