I’m findjng this incredibly frustrating. Since the update my events are finishing before my team does, sometimes way before. I have three teams and if I use gems to play rather than the free play, it seems to play out to the end. (Goes to level 28 at the mo.) But with each day’s free play it ends anything from level 18 up to 25. My team still has a lot of health left, the game just decides to end and give me the crystals or whatever for the amount up to when it ends. I turn the skills off auto around the time the third team starts, but that doesn’t seem to correlate in any way. there’s not much else I can see, it seems random, except it always happens with my final most powerful team. I’m losing a lot of valuable stones gems etc with this crash and it’s super frustrating!
I think it may be by design. There may be a maximum number of rounds based on your team’s power. I think the reason for it is to stop teams who concentrate solely on healing from getting stuck playing for many hours with little ability to kill or be killed.
For me, it’s now happening if I survive just over 100 rounds. None of my heroes died in last night’s event. The event ended. It was a personal best.
In order to get further, I think I may need to focus more on damage output and less on healing. Maybe.
Just a thought.
I’m focused on defense and I get kicked out at round 105 ish
It was the same way before the update.
It kicks you out after 100’ish rounds .
Now I just put my strongest team on group 1. ( i avoid knights in that group . They are tanks that barely do any damages & consumes way too many rounds)
My group # 2 sucks but they can squeeze an extra round if I’m lucky
I didn’t realize what group #2 was intended to do until today. I’ve been missing out on watching them get slaughtered in that extra round, because it would take a miracle for them to win against even 1 monster who was near death! 
Ok, thanks! I just thought it was me. I’ll do some restratagising.
Don’t feel bad i only figured group 2 out a few days ago.
Much better to figure it out now than 6 months from now!! 
Now we just need to figure out if the maximum rounds before the event ends is reset for each group.
If it is reset, then it would be a very good idea to put the weak team in the first group and the strong team in the 2nd group.
And if that is how it works, I would be much more willing to make my weak team a little stronger. Might even eek out a few extra victories before the strong team even starts. 
If that’s not how it works though, then the strong team definitely needs to go first. Otherwise, the weak team would waste precious rounds merely wounding monsters and dying.
Na, I had three groups, weakest first, but they were actually quite strong and lasted longer than the strongest group. So I think it “finishes” around round 105.
So now I have my strongest group first. I get much higher.
Good to know! Strongest first it is! 
@ trisen You were too busy farming pet fragments. My team had the “chance” to meet you in the arena & we got murdered lol
Good to find this post. The tip about putting strongest first definitely made difference. But not sure why the reward for one of the stones was lower when I got almost double the rounds…
Another Tip is to press cancel for the warrior and knight rather than use the the ward or skin until they cannot kill in one hit.
You can do it for the priest too until they first hit back about round 16.
This means you maximise the most of each round to move up a level.
There’s a wide random range but over the long-term, the further you go, the more you get.
Good tips, by the way. The priest and warrior should definitely focus completely on offense at the start.
Here are three more.
- At the beginning, save up the mage fireballs for when they can make a difference, Since one fireball can potentially kill two, it can get an extra kill right when the warrior no longer can. So, one mage kills two, the other kills one, and the priest and warrior finish off the 4th. Can save one or two rounds, sometimes.
- Sometimes, it is better to not use the fireballs if it lets the priest get the last kill. That way the priest’s Holy Shield will get one more round to cool down.
- When healing a hero with Holy Shield that heals two, never heal the most injured directly. Heal another that you want healed instead. The bonus healing will heal the most injured anyway. By picking another hero to heal instead, you get to choose who that will be.
Thanks for those tips… hadn’t considered the priest one before . Brilliant 