We are 3 friends in a minecraft forge server hosted by me. When connecting to a server with SWIAF, me and one of my friend can't connect to the server but the second one can connect, the bug is caused by the "swaif:dread_stone_stairs" that are with corrupted textures for my friend and I in solo world but not for the one who can connect. We have the exact same mod, for the server and our MC instances, same for the forge version.
P.S.: Joined a screenshot of the log when the error happend.

Hope you can help us !

This is a known issue. Earlier in development I changed the mod's id from "spartanfire" to "swiaf" which helped some people, but apparently not all. Nevertheless, this is an issue of the Ice and Fire mod which already has a fix but it's not released yet.