What could cause a buck controller to regulate to half its set point?
It's distinctly possible that the enable pin is actually controlling the setpoint of the converter. Pull it down, and the setpoint becomes zero. Pull it up to 1V, and the setpoint becomes whatever the internal reference is. It's imaginable that the damage is to the internal amplifier or reference or pullup rail, in which case the setpoint will also be different.

Obviously this is just speculation. But I'd be curious to know what happens if you force the enable pin to 1V with an external source.