Upgraded from 5.6.7 to 2017.4 and iOS lags and locks up

My application was working fine in Play mode, WEBGL deployment, Android, and iOS on 5.6.7. However since upgrading to 2017.4 my application locks up when it tries to do 3D on iOS platform only. I have confirmed that I can reinstall 5.6.7 and it works correctly, but this takes a lot of time if I have to do this every time I deploy. There is no error message on build or run, but any of my 3d scenes lag incredibly to the point that they are not useable and never complete. I can send a video from an iOS device if this helps. I think it is related to IL2CPP, I have tried all the recommended settings from the forum.

 

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