Because… Why not?
Star Trek: The Next Generation ‘The Royale’ just started. Geordi says the planed it -291ºC. That’s impossible because absolute zero is -273ºC. (I’ve also noticed that he’ll say ‘degrees Kelvin’ or ‘Kelvins’ instead of just ‘Kelvin’.)
It is very cold…in spaaace.
When they recalibrated the warp factor scale, they recalibrated the Celsius scale?
Work with me…
This one’s from the very beginning: there is no way, even when humans are capable of interstellar travel, that they wouldn’t be doubled over with laughter at the sight of an alien with a head shaped like a butt.
In “The City on the Edge of Forever” there is a sign for a fallout shelter a full decade before the first atomic weapon was built.
Well, it is just handwaved away, but traveling faster than the speed of light is impossible and will remain so.
So they’ve gotten to you too!
At least they didn’t come in speaking of making the Kessel run in 12 parsecs 
I prefer the original fan wank of that line- Han is just speaking gibberish to snow what he sees as two country yokels who won’t know better. He has no idea he’s speaking to a Jedi who has been all over the universe.
And the little eye-roll that Alec Guinness gives in response is absolutely perfect.
True, it is impossible, but I think that warp drive warps the space-time continuum and so it ‘folds’ faraway places so that they’re close together. Somebody please check me on that but I think that is the concept of warp drive?
In the TNG episode “Starship Mine” the Enterprise has to be evacuated to undergo a “baryon” sweep. All atoms are made of baryons so a sweep that got rid of them wouldn’t leave much left of the Enterprise.
You can’t route anything through the deflector shield except deflection.
Also the TNG episode “Genesis” has a huge amount of inaccuracies about genetics and evolution. I am not going to recount them all here when the TV tropes recap mentions most of them:
https://tvtropes.org/pmwiki/pmwiki.php/Recap/StarTrekTheNextGenerationS7E18Genesis
The unit was “degree Kelvin” for a long time. (Checking Wikipedia, it says until 1968.) So a valid nitpick, but understandable. I actually caught my high school science teacher with the same error.
As for “kelvin” vs “kelvins”, I always say the singular, but I can’t really complain because I use the plural “newtons”. It’s not clear to me what the correct form is other than the usage I’m familiar with.
Edited to add. The unit “kelvin” hasn’t been capitalized since 1968, either. So, you’re just as out of date. 
The TNG episode “The Next Phase” -Geordi and Ro are phased out of sync with the rest of the universe due to a teleporter accident. They can see everyone else but nobody can see them, And they are intangible and can walks through walls and other solid objects.
However–like many works of fiction that deal with intangibility–they miraculously manage to NOT automatically fall through he floor and walk around normally.
DOH! (In my defence, I’ve only used ‘K’ when writing a temperature, and Kelvin when writing the guy’s name. (OK, William Thomas, Baron Kelvin.)
In “Court Martial,” Kirk has the ship’s auditory sensors boosted “on the order of 1 to the 4th power” in order to find the heartbeat of a guy.
Some stuff can just be not what we’d expect, and have some sort of Treknobabel explanation we aren’t privy to. But that one is just obviously an inaccuracy.
Even more miraculously, they continued to breathe air molecules they were no longer in phase with.
And how can they see without being seen? Surely any photons that strike and interact with their retinas should be unavailable to strike anything behind them. If they’re seeing, they should be opaque and casting shadows at the very least.