A big problem that a lot of screenplay writers have is that they describe actions incorrectly. It's just something that they have to learn. The big rule that they break is that they describe actions in ways that cannot be recorded by the camera. An example of this can be found on the first page:
"It's an abandoned hangar (not 'hanger'). It's run down and rusty, but the equipment looks recent. But something doesn't seem right."
'But something doesn't seem right?'
There are other examples of this but, since I can't cut and paste from a pdf file, I'm not going to retype everything. The point is, the camera can't film this. You have to visually describe how something doesn't seem right. How the character behaves.
I felt that your dialogue was too on-the-nose. The characters were straight to the point, as if you were limited to how many words to use. No one talks like this. Stretch it out a little bit. Pad it. You should especially add to the explanation that Eric gives regarding the shadow creatures. It was so cut and dry that it was unrealistic.
Read some other scripts on these boards to see how dialogue is written.