I am in my second game in shattered plains first over 2 hours and now I am at over 300 waves and in both games I did not get knux. Maybe it was just bad luck but I don’t want to make study for this;)
I started both nature only with solara as skill pick. When I had enough wolves I used darkness potion.
Seeing as (at least from my perspective) knux is a very important tower for long games with any carry, I am about to lose the 2nd game.
On a side note I want to question the balancing if knux is so essential as I see her.
No it's not a bug, it is not guaranteed that all towers drop in every game. In fact, by adding more towers the odds to get a specific one are getting worse.
What I heard is that you can work around not having Knux with armor reduction items, e.g. Cactus.