Shattered Kingdoms

You give a dryad's tentacle to Amertith the huntress.
[HP:100%] [ME: 20%] [PE: 97%]
>
Amertith the huntress inspects the item, then tucks it in her quiver.
Amertith the huntress says to you 'Good! You need to exteqmimate 23 moqe of them'
[HP:100%] [ME: 20%] [PE: 97%]
> give tent woman
You give a dryad's tentacle to Amertith the huntress.
[HP:100%] [ME: 20%] [PE: 97%]
>
Amertith the huntress drops a dryad's tentacle.
Amertith the huntress junks everything in the room.
Your pulse slows to normal.
[HP:100%] [ME: 24%] [PE:100%]
> give tent woman
You give a dryad's tentacle to Amertith the huntress.
[HP:100%] [ME: 24%] [PE:100%]
>
Amertith the huntress asks to you 'What is that?'
[HP:100%] [ME: 24%] [PE:100%]
> give tent woman
You give a dryad's tentacle to Amertith the huntress.
[HP:100%] [ME: 24%] [PE:100%]
>
Amertith the huntress inspects the item, then tucks it in her quiver.
Amertith the huntress says to you 'Good! You need to exterminate 22 more of them'

The dropping and junking is a script on the NPC that allows it to continually take more. It's basically a safeguard against the quest being undoable until the tentacles crumble.

The second part where she doesn't recognize the tentacle is likely because the dryad NPCs occasionally drop tentacle body parts that are not meant to be turned in for the quest.

I am aware of those tentacles and they are greyed out.

This particular one was red and green, the quest item's color
and it appers like:
You give the tentacle of a blood dryad to Amertith the huntress.

Thank you though

This can happen sometimes when you give to them right at a tick.

Might be the case as I've delivered more than 300 tentacles.

It only happened once

That's what it is. I've noticed it happen on many other "give me x amount of that" quests. Giving one right on the tick does not register for the correct item.

That also happens when you give a sliced off tentacle instead of a quest tentacle.