(at around 12 mins) When the crew of The Harbinger raise the 'object' shortly into the film, they claim it is encased in 'old ice' (due to the visible blue colour). Indeed, due to compression over many hundreds/thousands of years by 'newer ice' forming on top, this would be the case. However, according to the opening sequence; the object/craft in question crashed in 1982, and would unlikely have been there long enough for the necessary ice build-up and compression needed to give it the blue colour.
In the opening scene, the Soviet LK spacecraft is returning from its moon mission with its landing legs attached. The landing gear would have been left behind when the spacecraft left the moon.
The spacecraft is discovered underwater because of a red blinking light (which continues to flash after the capsule is moved to the ship's hold). No battery/incandescent light system from 1982, especially on a ship designed for lunar transit, would continue functioning more than 30 years after the crash.
(LED's did exist at the time but were not yet powerful enough to be used as illumination, rather they were used as indicators on calculators and other electronic devices.)
(at around 1 min) The coordinates in the opening scene, 58.122 N -178.603 W, are not in the Arctic Circle but south of it in the Bering Sea.
(at around 20 mins) Ronelle asks if anyone has cell service, to which Sadie responds, "it's the storm." Maybe Ronelle wouldn't know, but Sadie, who is familiar with sea travel, would know that you cannot get cell service in the middle of the ocean, storm or otherwise.