Diablo 4 - BUG - Hatred's Hoard: Infinite Event?

Last night, I stumbled onto something strange—or maybe incredible—in Diablo 4. I was inside the seething realm at the Hatred's Hoard event where the goal is to defeat waves of enemies as fast as possible to earn more chests. Normally, I am only able to reach three chests within a minute or so, and I was never able to earn chest #4 but this time, I decided to push it to see what would happen if I kept going. Well, I reached "Chests Earned: 13" after almost 2 hours and decided to quit without getting any reward and well... It was a waste of time!

I firmly believe now that this is a bug, specially because despite killing so many monsters I got 0 XP and because every new "Chests Earned" wave that spawns, it takes much more longer to complete than the previous one. But again, this is Diablo 4, and what if I was wrong and there was something legendary waiting beyond at chest 15, 20 or higher? Or what if this is just a bad joke? I will never know.