AI activates Distorting Lens at any opportunity it gets, often making nonsensical choices of color and targets. I can provide a decklist if it would be easier to check, the behavior is exceptionally erratic.

It's a lot like how if the AI playes Shifting Sky with nothing relevent to it in hand or on the bf it will pick a random color. The exceptional factor is that the targeting with Prismatic Lens seems erratic, so it causes follow-up removal with Northern Paladin or Celestial Purge to seem erratic too.

EDIT: This behavior MIGHT be caused/made worse by having Northern Paladin and Celestial Purge in the deck/hand, though, as they can target permanents. What I've seen several times is changing the color of the players land and not following it up with the Northern Paladin activation (although I've seen it destroy lands with Celestial Purge).

EDIT2: Although it's still just doing plain weird things like targeting one Prismatic Lens with another copy of itself it has on board and similar.