Special Event Is Unstable

Hi, anyone of you have troubles playing that special event Wave 20/20 ? I keep having myself getting boot out of the waves, I was playing halfway at waves 8/20, sometimes 9/20 or 11/20, suddenly I got boot out of the game.
When I returned, I have to start over again.
There is something wrong with the special event, please fixed the bug as soon as possible, keep getting exit out of the game suddenly and have to start all over is not fun..