Game runs at 60FPS with Oculus Rift on OculusVR on Unity 2019.1

We recently decided to port our VR game from Unity 5 to Unity 2019.1. After the port we noticed that standalone build of the game targets 60 FPS on Oculus Rift + OculusVR. This is out of sync with the device's refresh rate and causes all movement stutter badly.

We have tried several 2019.1 versions with Application.targetFrameRate set to -1 and 90. In all tests the fps will be 45 or 90 for a short while after starting the game but after ~20 seconds seconds the fps will lock to 60, which is very very bad. Application.targetFrameRate is -1 (or 90) while the game actually runs at 60.

Using Oculus Rift with OpenVR works perfectly: the game runs at 90fps and all movements are smooth. Also, the game doesn't start targeting 60 FPS in Unity Editor but only in the standalone build.

More details: - Unity 2019.1.f4 - Oculus (Desktop) 1.36.0 - OpenVR (Desktop) 1.0.5 - The game is Premium Bowling, been months in Early Access

Seems to be a bug in OculusVR. Ideas, anyone?