I tried Opus first. It figured out that there had to be tangential frictional forces on the lower balls, but asserted that there was no frictional forces on the upper ball "by symmetry". From this, it deduced that the lower balls would have a torque and would thus start spinning at higher and higher angular velocity. It noted that this would violate conservation of energy, but didn't seem much bothered.

Fable 5.1 did a much better job and paid attention to warnings about tangential friction. It correctly noted that the critical coefficient for friction was at the contact points with the upper ball. It also pointed out that a ring around the balls at center height would hold them together even without ball-ball or ball-table friction.