20230109: Fixed strings are now strikethroughed. Also, I opened MCPE-165888 with new mistranslations.

There are lots of wrong translations.
After some Ctrl+F-s, I've found these and I am sure there will be more.
(From my point of view - as a participant of JE Crowdin - there are many other strings that require some proofreading or have better translation, but here I'm listing obvious errors only.)

Original string => Wrong translation(Wrong meaning) - Comment

Smelt an iron ingot => 철괴를 녹이십시오(Melt an iron ingot) - Melting and smelting is different. Should be 철괴를 제련하십시오
container => 보관 장치, 컨테이너, 보관함 - inconsistent. 보관함 means Inventory in JE
Every 'End' is replaced with 'Ender', except '엔드 스톤'(End Stone). Please do not.
Redstone Repeater => 레드스톤 탐지기(Redstone Detector). Should be 레드스톤 중계기
Knockback => 타격 반동(Rebound. or Recoil) - JE uses 밀치기(Pushing. Shoving)
Silk Touch => 채굴 정확성(Mining Accuracy) - JE uses 섬세한 손길(Delicate Hand)
Feather Falling => 낙하 방어(Defense against Falling) - How am I supposed to 'defend' against falling? // This has been changed to 깃털 낙하, which literally Feather Falling. But this sounds so unnatural so I don't consider this fixed. JE uses 가벼운 착지(Light Landing).
planks => 목재, 판자 - inconsistent. JE uses 판자
block => 블록, 블럭 - 블럭 is a spelling error. should be 블록
ocelot => 오셀롯 - spelling error. should be 오실롯
spruce => 전나무(Fir) - different species. should be 가문비나무(spruce) // Mostly changed to 가문비나무, but an inconsistent string remains.
Stray => 야생동물(Wild Animal), 야생 스켈레톤(Wild Skeleton) - JE uses 스트레이
Ground Cover => 지면(The Surface of the Earth) - should be 지피 식물
Shear (Mooshroom) => 털 깎기(Shear Fur) - There is a separate key for shearing sheep. should be 버섯 깎기(Shear Mushroom) or 깎기(Shear)
Enchant(ing/ment) => 효과부여(Give-Effect), 마법부여(Enchant), 효과 부여(Give Effect) - inconsistent. JE uses 마법 부여
operator (permission) => 연산자(operator in math) - should be 관리자
Drowned (entity) => 가라앉음(has sunk) - This is a mob, and should be translated accordingly. JE uses 드라운드(sound translation), following the consensus "Entities which are not present in the real world are sound-translated." among Korean translators on Crowdin.
Spawn Drowned (spawn egg) => 생성지 가라앉음(The spawnpoint has sunk)
Comment (user-generated content) => 덧글, 댓글 - inconsistent. should be 댓글
is useful for guarding portals => 경계 포탈을 만드는 데 적합합니다(is useful for making boundary portals) - should be 포탈을 보호하는 데 적합합니다

Also, according to the glossary, these strings should not be translated.
Endermite => 엔더 진드기(Ender Mite) - Should be 엔더마이트
Mooshroom => 버섯소(Mushroomcow) - Should be 무시룸
Purpur => 보라보라(Purplepurple) - Should be 퍼퍼

These translations are not following the translation guidelines provided to the JE translators. I strongly suggest unifying these with JE.
Conduit (mythical item) => 도관 (Conduit, Pipe in real life) - The literal translation should be avoided. JE uses 전달체, which is a pretty good translation following the guideline.
Conduit Power => 도관 동력 (Conduit Power, brings electricity to mind) - Guideline: "Should NOT bring electricity to mind.", JE uses 전달체의 힘

If this team's going to continue translating Minecraft, they should make greater efforts to check the keys of the strings and create some kind of standard or guideline to make the translation consistent. And it would be far better if Crowdin proofreaders like I could proofread the translation.

+ I wonder whether the same team translated commercial usage guidelines. In 2016, I found five translation errors in a single section 'Servers and Hosting'. The license and guidelines need proofreading too.