It could be that a static discharge killed the pull down circuitry, so the floating pins may not be a $A0 anymore.

I had in the past various issues with static and decided to be almost paranoid with this thing. Have anti-static mate on the floor, also on the bench and I earth my self too. Of course the soldering iron is earthed too by a tens of kΩ range resistor.

Chips from various vendors also have differences and datasheet may not cover that. Richard is right.

Ioannis