Those who are participating in the Breakthrough event can't complete Lv 140 & 150 mission once they hit 160 because they can no longer enter Intermediate Monster Park. Not to mention that they cannot accept or complete any more missions because they haven't done the previous quests.
Too harsh of a punishment for overlevelling, don't you think?
To those of you who think people are overreacting and should just patiently wait:
1. Get a part-time job at a restaurant or something
2. When a customer comes and orders his food, tell him that it will be done in, like, 20 minutes
3. After 20 minutes, go to him and say "Oh I'm sorry sir, but there was a problem with the ingredients and I'm afraid that you'll have to wait for a bit longer - but I cannot and will not tell how much longer it will take"
4. After the food is prepared, take it to him - but then throw it away and say "Oh I'm sorry sir, but there was a problem with the food and I'm afraid that you'll have to wait for another few hours - but I cannot and will not tell how much longer it will take"
5. If he complains, then say "Dude, it's not the end of the world. Obviously you have no idea how difficult and time-consuming cooking can be. Grow up, be patient and do something else while you're waiting"