Probably a lot of people are experiencing what you are without realizing it. I had cataract surgery several years ago, and since they don't want to do both eyes at the same time, you go through a period of time where you wear your glasses with one lens in and one lens out. Makes it interesting to shoot, to say the least. It's really obvious when your dominant eye becomes blocked by your nose.
What's not so obvious is that when both eyes are functioning normally, if your dominant eye becomes blocked, your other eye takes over, which can cause you to miss the target and you don't know why.
The answer is to rotate your head enough toward the target that your nose doesn't block your dominant eye from seeing the target. That's the only answer (sorry Terry for the absolute, but it is). If you can't rotate your head that much, then you have to stand more open to the target so you can. Maybe it's not ideal to stand open to the target, but it's essential that you see the target with your dominant eye.