Hi,
I have started to develop a game in UE4 4.27.0, for iPhones, at that time the IOS version was 14, everything was working correctly on phone and in the editor as well.
After IOS 15 update I couldn’t deploy the game on the phone, UE4 4.27.1 solved this issue, but since the updates the game lags every 2 second!!!
There are moving actors in the game and in the movement they stop every 2 sec for a moment and continue moving, which is so annoying because it is based on moving parts. I even tried with only one moving object… same issue.
So in the last 3 months I have tried to solve the issue, but I started to give up. In the editor I have no issue, it seems something happening during the cooking process.
Is it a bug or I miss something very basic settings as usually do 
?
Thanks