Infinitely spinning particle?

Hello,

I have a single particle resting on a plane which I then set spinning. The particle experiences a constant angular velocity, despite an opposing torque (attached plot). I create the particle on top of a primitive wall and allow it to settle before setting omega_z to 1 m/s. With rolling friction (EPSD) on, there is a small but constantly decreasing z torque, however the particle's omega_z remains at 1m/s. What to do I need to fix about my script (attached) in order for the particle to see a decrease in angular velocity over time? Thanks!

Eric