WTF with the ending?

It's a quick shot, not obvious, but as the two crew members- the guy with Calvin (hoping to sacrifice himself into outer space and freeze the alien) and the female (to try and land safely on earth and warn mankind)- eject into space, their trajectories send them into space debris and their paths swap.

So now, as revealed as the Chinese/whatever fishermen approach the landed craft, instead of it being the female astronaut, it is David and a much-grown Calvin.

It's an illogical twist. It's a failure from the director. No need to explain it, the director just tried something and it didn't work.

Total cheap move/fool the audience 'twist'

Lame

a twist which opened the door to a potential sequel... i thought it was ok not cheap or bad, just a small wtf shock

I thought the ending was great.

It wasn't illogical...just an catastrophic 'gotcha' moment.
The audience assumed the girl had made it back and that the guy (and alien organism) were banished into space...cue happy ending...roll credits.

Except it didn't pan out that way,

I felt the intended sense of dread as the fishermen closed in (unaware of how fatal their kind actions would be) and I'm normally a sucker for Happy Endings.

I really enjoyed this movie (and it looks amazing in 4K)

They also explained it. The escape capsules were programmed to automatically return to earth without a manual override. David was planning to fight and resist the creature and hold the manual override for as long as he could, hopefully long enough that the capsule couldn't return to earth. But the creature broke his grip on the controls and the automatic protocol took over before he got far enough away.

Miranda's capsule malfunctioned in the launch. The direction just obscured which capsule was which until the last scene.

What a downer ending though.