After having verified machine was level, and walking through a reset with Samsung tech support, the machine still wouldn't stay balanced (stopped during spin and displayed "dc" code).
I replaced all four suspension rods as described in the appliancepartspros.com video.
Our machine was only three years old. However, I learned the design of this machine is somewhat prone wearing out these rods. If you put heavy loads of absorbent fabric in the machine, the weight in the spin cycle is significant, as it has a large tub and uses a water sensor by height of the water to determine when to start the spin cycle.
I saved $200 by ordering from appliancepartspros.com and doing it myself.