Steps:
1. Build and Run user's attached project ("ios_frame_stutter_repro.zip") on mac

Result: notice how frames are stuttering.

Reproduced with: 2018.1.0b4, 2017.3.0p3, 2017.2.1p3, 2017.1.3p1.

Tested with:
MacBook Pro 2015 (macOS10.13) - reproduced
iPad mini 4 (iOS) - not reproduced
Samsung Galaxy S8 (Android) - not reproduced
Surface 3 (Windows) - not reproduced

Notes:
-both openGL and Metal are affected.
-the stutter is not seen in recorded videos (QuickTime > record screen) and screenshots (cmd+shift+4) but it is clearly visible on the screen.