Early in the film the Fifield's 'Pups' (The red survey balls) are released to map the structure. After they have done the mapping one of them stops at the end of a passage.
We later discover this is the entrance to the Alien Spaceship, or perhaps a door within the spaceship.
Later when Milburn and Fifield are stranded in the pyramid structure after becoming lost trying to find the way out, Janek (back on the ship) notices that this pup is "pinging" a life form. But not consistently so they suspect it was a glitch in the pup.
Is this pup picking up the engineer in the stasis pod? If so what accounts for the inconsistent nature of detection? If not, what Life-form is the pup detecting?