More on this.
The diagnostic codes indicate load balance issue, motor fault and shifter fault. However, the motor works fine for everything except low speed spin so I assume it's OK. When I do the low speed spin test, I can see the shifter engage and the tub starts to spin for a few seconds. Also, it works fine on high speed spin. So, I think the shifter is OK.
So, what else? The main control unit?
I see online that there are recommendations to check the drain filter for spin issues but I can't find a drain filter on this model. Also, it seems to drain OK, although, I can hear a bit of water swishing in the bottom when I shift the unit.
I'm stumped. Control units are expensive and I don't want to buy one unless I'm sure I need it.