Ring Doorbell 3 Motion Detector not working well

Hi, My original Ring doorbell worked pretty well but it died, so I just installed a RIng 3 doorbell. I used the corner mount because of the location of the doorbell and the video is actually much better. But the motion detector doesn't work when someone approaches the door. It DOES work when I come out of the front door (which isn't very useful). I have it set to max sensitivity Is there something I can do about this? Or do I need to mount it straight (which might sove the issue but I may not get as good video)