Video doorbell pro sensitivity and wifi connection

I recently got a video doorbell pro and am disappointed in the performance. Sometimes the camera is sensitive, sees a car going by (very little traffic where I live); other times it misses someone dropping off a package on my porch. The wifi is very weak. I measured the signal at the spot where the doorbell is mounted and it's strong, around -40db. I added a wifi extender less than 10' away. Still the connection test reports approx. -60db. I've uninstalled and reinstalled it. That's all the patience I have for it. 

So the question is: Is this usual behavior or do I have a lemon?