Sometimes I'm starting to climb in the air, the only way to fix this I found is to reload the server, but reloading the server can also cause this to happen again

That's really weird. Could it be that there are some bugged vines in the air?

No

This also happens when I'm just jumping

Wait no Vines don't even have the animation. It only happens when the client thinks it's climbing and on a ladder/trapdoor. Could only be that something is messing with the data, either another mod or the server, which I doubt it can do that (Don't think the server can put players into a climbing state like that).

Well, I have a lot of mods in the modpack...

https://github.com/tr7zw/NotEnoughAnimations/blob/main/src/main/java/dev/tr7zw/notenoughanimations/animations/fullbody/LadderAnimation.java#L35 The code checks if the entity is in the climbing state, not on the ground and the last known climbing block was a ladder. These are all vanilla values. And apparently onClimbable is stuck to true, that would also explain that the animation happens during jumping.

Wait, I just noticed that climbing animation looks a bit different

Could be, that it's some other mod/Animation resource pack.

Ok I'll keep searching for problem source, thx

I mean, try turning off the animation in the settings/removing NEA and see if the issue still happens.

Ok

yup... it's now playing animation from another mod when I'm using ladder
and this animation is being played when I'm in air

Sorry for reporting this, and thanks for helping

No problem

It was Personality mod if you mind