Weird comfort access behavior

[vx5_48i]

I have seen this happen a few times, I am either loading something up in the back and leave the tailgate open and I go set the key in the cup holder and I try and start up my X and I get the key with a slash through it, key not detected, when the key is right there in the cup holder but when I go close the tailgate I can then start it up.
Also happens when I could be sitting in the driver seat, car on, key in my pocket and someone else opens the tailgate I am then slammed with gongs and warnings that the key is not detected and after the tailgate is closed the warnings disappear so I figure the key is detected again.
I have never been warned that the battery is low, I just replaced it to see if it would help with this behavior and it didn't. I'm not sure what this sounds like if its a key issue or an antenna issue.
I dont have any problems getting into the car or locking it.
Doesn't make sense to me since I have noticed that I have to be pretty far away from the car with the door closed while the engine is running for the key not detected warning to come up.
Does it sound like an antenna issue or a key issue?