ARKit SDK Face Tracking performance issue.

Hi There,

The camera feed and ar tracking are laggy in our app. We tried to check the FPS of the app and find its mostly not related to the camera / tracking issue. The app runs at 60fps but the camera is very laggy that makes it look less than 24fps. We are often experiencing crash issue and having a bunch of this error log on XCode:

Execution of the command buffer was aborted due to an error during execution. Discarded (victim of GPU error/recovery) (IOAF code 5)

Device: iPad and iPhone X (iOS 12)

We also tried to update the Unity version from 2018.2.9 to 2018.3.10 then we rarely see the XCode error mentioned above but the camera and face tracking lag still persist. Also tried to create a new empty project and transfer the assets there, but it didn't solve the problem.

Now we are looking into using the AR Foundation instead but after looking at the documentation it seems that there is no access to the ARKit's face blendshape values like jawOpen, eyeLeftSquint, and etc. The app is supposed to display an AR object on the user's face and the object reacts based on the user's facial expressions.
Is there a way to improve the performance in ARKit, or get those ARKit face tracking values in AR Foundation? Does AR Foundation run smoothly on iOS 12?