BUG: iphone face capture has problems with eye tracking

[sena-nana]

what happend

When I use the iphone face capture, I notice that when I try to squint, the capture parameter changes dramatically from 0.4 to 0.This prevents me from making fine eye movements.

what I try to do

1. I tested both camera capture mode and Nvidia capture mode as well and neither had this problem
2. I also turned on prprlive, another facial capture software often used by Vtubers. Both applications use the capture mode of the iphone at the same time, but prprlive does not have this problem
3. I tried to capture using the iphone side without connecting to the computer. The problem is the same, but better. The parameter jumped from 0.25 to 0
4. I asked friends who also use iphone face capture and they said they also encountered this problem. This may not be an isolated case but a common problem
5. I have tried modifying the sensitivity and value mapping, but the wrong value seems to exist from the face algorithm stage and my attempts have had no effect

guess

I suspect that this problem may be caused by the core algorithm of the iphone capture mode

my env

iphone: iPhone XR (My friends also uses this model because it is the cheapest model with Faceid support)
vtubeStudio: stable version installed from steam

I have used translation software, if there is any ambiguity please let me know and I will explain in detail