Reproduction step:
1. Download and open attached project
2. Make sure that the graphics option "Auto Graphics API for Mac" is checked.
3. Make build and create new account with dummy profile.
4. Play any song
5. Compare with high sierra

Actual behaviour: Stuttering happens intermittently during the song playing.
Expected behaviour: Gameplay is smooth with no stuttering.

Note:
Only reproducible on Sierra. Not reproducible on High Sierra.
The frame rate observed is still 60fps.
Please watch the video closely to notice the stuttering.
This issue is observed only on older MacOS devices, did not manage to reproduce on new ones.
Also, when switching back to using OpenGL, the issue is gone as well.

Reproduced with 2018.3.0a6, 2018.2.0f2, 2018.1.9f1