Had that problem as well. What I did to fix it is everytime it couldn't see me and wanted to enter a pin and logged on I went to settings and did the improve facial recognition. When I set it up I do facial recognition straight at the camera, tilt it and have it catch me looking from above, and then do a looking right and looking left scan. I do one in ptch black and go outside and do one when its bright and to top it off I do one with a hat. With that it now gets me every single time no matter what. Might take a few mins but well worth it.
Taking that extra step really does help. It did wonders for me after only doing it twice.