Neither the D500 or D7200 should underexpose. If they are both doing it, I am sorry to say, sounds more like piolet error than equipment failure.
You may want to really pay attention to what you are shooting, matrix metering is always a good thing. Next time your out, with the sun behind you, take a reading in Manual of the green grass in front of you. Green grass reflects about the same amount of light as a gray card, Close enough anyway to check your reading.
Now raise the camera and take an image, it should be perfectly exposed, or very close.
Next, with the camera on matrix metering in say aperture priority, take an image of the lawn with the sun coming in over your shoulder.
If, under either conditions, your shots are under exposed, then call Nikon at 1-800-645-6687 and ask for tech support.
Or, the next time your in Palm Beach county in Florida give me a private message and I can help you out with a free lesson.

Approximately three weeks ago I received a new Nikon D500 and posted on this forum the focusing issues I was having with it. I will say it locks on focus rapidly with most subjects but has problems with others. For instance yesterday morning it was having a problem with locking on focus on a sparrow on the ground. BUT here's the great news: it is performing perfectly and even exceeding my expectations on the type of shots I purchased it for and that is birds in flight. With my D7200 I was having a problem locating birds in flight looking through the viewfinder which was very frustrating but with the D500 focus locks on instantly once that bird is in the viewfinder area. Evidently with the D7200 once the bird was in the viewfinder area it would be out of that area before the camera had time to focus. In my opinion the image quality from the D500 is no better than from the D7200 but I'm okay with that because that was not my reason for purchasing it. My decision to purchase the D500 came from a trip a friend and I took to Reelfoot Lake in Tennessee to photograph bald eagles. She was shooting with a Canon 80D and was having absolutely no problem locating them through the viewfinder as they were in flight whereas I was struggling. I thought perhaps the reason for that was the increased light hitting her sensor from her f/2.8 lens so I started researching lenses but didn't want to spend thousands of dollars on a faster lens so decided to go with the D500 to see if that was any better and fortunately it is. Shooting birds in flight now is a pleasure instead of a frustrating struggle.

Yes it is supposed to in spot or center weighted metering. The spot is almost impossible to keep on a bif. For most of my bif is shot manuel with auto ISO and matrix metering. If it's bright out I'll set ISO to 100 and overexpose by a stop or so. It will blow the sky but the bird will be good. I also shoot in raw so I can edit the shadows if need be and dim the sky in post if needed. I try not to shoot bif against the sky. It's just boring to myself. Matrix works great for me if not against a barren sky. I personally find it almost impossible to use spot metering on a bif.