I think this is related with balor glitch...
I had built everold's workshop while playing main questline, and I have been played successfully before facing balor.
But I had experienced balor glitch, so I used the method below;
I deleted dlc_35 folder in order to get gae bulg, and recovered that folder after i get that spear.
However, everold's workshop has been disappeared after I used this method and it's still remaining in this state.
I tried to recheck game files for several times but it didn't worked at all.
Please help me.