You get the 4th box with your 10th win.

Seriously?

That box should be triggered at the 4th win, not the 3rd, not the 5th, not the 10th. 99% of the time I don't have time to play for 10 wins.

Another bugged event. Great. *sigh*

No. It has always been like this.

Is this the first time you play such an event?

You need to take a few seconds to read the event notes properly:

1st box at login, 2nd box at 1st win, 3rd box at 4th win, 4th box at 10th win.

There is nothing "bugged" here.

Not really. YOU need to read my post or the event notes better. i did no receive the box for the 4TH WIN (the 3RD box in your logic).

So, on the contrary, it is bugged.

 third box is difficult, imagine the 4th, you have to win more than 4 battles and stay to the end ... no 5 min. and more than 10 for the 4th box. the pagfina wrong and have done nothing to look at that

Were you sure to wait the 5 minutes and also do at least 1 attack and be in an elegible room (Not normal, mission or HA)?

I do get my 4th win box when this conditions are met.