Rank 3 4* against boss rush.

Ohk so I have 5/50 4* , but no good bleed immune champ , so I used my 4* 3/30 ghost rider against blade . Not sure why but the control was not smooth at all , and also i used my dormammu , the game lagged like hell . I am pretty sure my phone works fine , so is this problem with 6* or the game AI .
P.S -I have completed the challenge .
P.S -I have completed the challenge .
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Comments
I suffer lagging (up to 6-7 seconds) on various battle backdrops, like the hangar (quinjet flies in, back off until it landed..), Rooftop, same thing, Hell's Kitchen where I have no clue what triggers it, all the Sanctum backdrops, Knowhere when that add flies up in the background. All on iPad. Never on iPhone. Not 6*, not AI, but scenery.
I guess this challenge was about suggesting any bug or something about the new 6* , and in nowhere in my post I asked for advice in completing challenge , I am just asking if somebody else also felt those bugs , so that kabam can rectify it .