Kill a Monster Park boss

That's Wednesday's Mission in the rainbow event.
So I went and cleared the Dead Tree Forest - and the quest didn't complete. Not only that, but Spigelmann's daily "Great Fun in the Monster Park" quest (which also asks to kill a boss) didn't complete either.

Have the requirements changed recently? Do I have to kill the very last boss? Or any boss over 150? Or is the quest glitched entirely?

I read that it has to be close to your level. 150+ would more than likely have to do SH or ToT.

I read that it has to be close to your level. 150+ would more than likely have to do SH or ToT.

Did ToT, and Lyka dropped a crayon piece. Picking that up completed the Wednesday Mission. I was solo so I don't know whether it's shared pickup (like the coins) or each person has to kill a boss of their own.
Spiegelmann, on the other hand, still doesn't believe I killed one of his bosses...

I did a quick Stronghold solo and got the Crayon Piece, as well as completing the Monster Park "Boss" daily.

The crayon is shared between all the members if the boss is lvl 150+, I went in a full pt where the lowest member was 141 and the highest 200 and we all completed the quest when someone looted the crayon.

Sometimes it doesn't count if you're in an expedition. Try going in a regular party.