Washer spins, goes "off balance", adds time - and this repeats. Samsung forums suggested: Door switch, bundle of wires loose and motherboard.
After searching specifically for this model, I found others have this same recurring "off balance/add time" issue. FINALLY, I found a YouTube which showed a similar model with the same issue.
Thankfully, we found the issue. The machine has four shock absorbers on the bottom. They needed to be replaced. This solved the "out of balance" issue during spin.