Short Description
well, i can't give much information, a friend hosted my personal modpack on his PC and as soon as i get inside the server it instantly crashes. (but he is already inside the server)

To Reproduce
Steps to reproduce the behavior:

1. Add my modpack on 2 computers, (if i recall correctly) one will host the server and run minecraft at the same time (PC 1), the other just needs to run minecraft (PC 2)
2. get inside the server in the computer that is hosting the server (PC 1)
3. get inside the server in the other computer (PC 2)
4. See error

Crash Report
Crash 1: https://pastebin.com/BmZiWx3s
Crash 2: https://pastebin.com/g8uecLUz

Additional Notes
i never had this issue before, i only played in singleplayer, maybe this is related to running the modpack on a server, but i can't test it by myself (or maybe its related to the other mods, TF2 Stuff Mod or Performant (sadly this one is close source, but if you think that it is the guilty mod i can remove it, in words of its author, "the 1.12 version of Performant does not much to increase performance")

EDIT: it seems that the second crash report changes the other mods related to the crash, maybe its more related to Survival Inc )

I just looked at it and it seems you're right. Damn how could I not notice it? As you said, it was that client-only constructor. I don't know which douchebag decided to mark it client-only. Well, it seems that I will have to unpack all those Vec3d-s to use the common constructor.

i have no idea if maybe this is related, but i wish it is:
BuildCraft/BuildCraft#3678

that issue is also related to an issue in Botania called "WHO THOUGHT HAVING A CLIENT ONLY CONSTRUCTOR WAS A GOOD IDEA!?!?!"

oh, ok, well, i will tell this to that friend, thanks

Just a side note, I came across more server-breaking issues when investigating this, so I recommend you to not use the master branch at this moment until it's fixed.

ok, many thanks, i will wait