Revealing mistake: After the Kree arrive on the ship, in a side shot one of them opens the lunchbox holding the tesseract. We see the blue light emanating from inside, but that only appears once the box is fully open - while it's opening, there's no light inside at all, despite the tesseract always glowing. A later shot shows the glow being visible around the edges of the lid even when the box is completely shut, and when Carol opens it later, the glow appears immediately.