Tapping lands inconsistent when copying opponents Nikya of the Old Ways

I have [[Volrath, the Shapestealer]], AI has [[Nikya of the Old Ways]] with a counter on it, turn Volrath into Nikya. Then lands are inconsistent on how much they produce when tapped, often producing 3 instead of 2.

First Island taps for 2:

2nd Island taps for 3:

3rd has tapped for 2:

4th tapped for 4:

Undoing the tapping, and then tapping a swamp has produced 4:

A 2nd swap has produced 3: